Imperial College London

Dr Koon-Yang Lee

Faculty of EngineeringDepartment of Aeronautics

Reader in Polymeric Materials
 
 
 
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Contact

 

+44 (0)20 7594 5150koonyang.lee

 
 
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Location

 

325City and Guilds BuildingSouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
to

91 results found

Goosens V, Walker K, aragon S, Singh A, Senthivel V, Dekker L, Caro Astorga J, Buat M, Song W, Lee KY, Ellis Tet al., 2021, Komagataeibacter tool kit (KTK): a modular cloning system for multigene constructs and programmed protein secretion from cellulose producing bacteria, ACS Synthetic Biology, ISSN: 2161-5063

Bacteria proficient at producing cellulose are an attractive synthetic biology host for the emerging field of Engineered Living Materials (ELMs). Species from the Komagataeibacter genus produce high yields of pure cellulose materials in a short time with minimal resources, and pioneering work has shown that genetic engineering in these strains is possible and can be used to modify the material and its production. To accelerate synthetic biology progress in these bacteria, we introduce here the Komagataeibacter tool kit (KTK), a standardised modular cloning system based on Golden Gate DNA assembly that allows DNA parts to be combined to build complex multigene constructs expressed in bacteria from plasmids. Working in Komagataeibacter rhaeticus, we describe basic parts for this system, including promoters, fusion tags and reporter proteins, before showcasing how the assembly system enables more complex designs. Specifically, we use KTK cloning to reformat the Escherichia coli curli amyloid fibre system for functional expression in K. rhaeticus, and go on to modify it as a system for programming protein secretion from the cellulose producing bacteria. With this toolkit, we aim to accelerate modular synthetic biology in these bacteria, and enable more rapid progress in the emerging ELMs community.

Journal article

Kondor A, Santmarti A, Mautner A, Williams D, Bismarck A, Lee K-Yet al., 2021, On the BET surface area of nanocellulose determined using volumetric, gravimetric and chromatographic adsorption methods, Frontiers in Chemical Engineering, Vol: 3, Pages: 1-12, ISSN: 2673-2718

Volumetric N2 adsorption at –196 °C is generally accepted as “gold standard” for estimating the Brunauer-Emmet-Teller (BET) surface area of nanocellulose. It is unclear however, whether the BET surface area of nanocellulose obtained at such low temperatures and pressures is meaningful at an absolute sense, as nanocellulose is used at ambient temperature and pressure. In this work, a systematic evaluation of the BET surface area of nanocellulose using a highly crystalline bacterial cellulose (BC) as model nanocellulose was undertaken to achieve a comprehensive understanding of the limitations of BET method for nanocellulose. BET surface area obtained using volumetric N2 adsorption at –196 °C was compared with the BET surface area acquired from gravimetric experiments using n-octane adsorption measured using dynamic vapour sorption (DVS) and n-octane adsorption determined by inverse gas chromatography (iGC), both at 25 °C. It was found that the BET surface area calculated from volumetric N2 adsorption data was 25% lower than that of n-octane adsorption at 25 °C obtained using DVS and iGC adsorption methods. These results supported the hypothesis that the BET surface area of nanocellulose is both a molecular scale (N2 vs n-octane, molecular cross section of 0.162 nm2 vs 0.646 nm2) and temperature (–196 °C vs 25 °C) dependent property. This study also demonstrates the importance of selecting appropriate BET pressure range based on established criteria and would suggest that the room temperature gravimetric measurement is more relevant for many nanocellulose applications.

Journal article

Yang Y, Wloch D, Lee K-Y, 2021, TEMPO-oxidised nanocellulose hydrogels and self-standing films derived from bacterial cellulose nanopaper, RSC Advances: an international journal to further the chemical sciences, Vol: 11, Pages: 28352-28360, ISSN: 2046-2069

Hydrogels derived from TEMPO-oxidised cellulose nanofibrils (TOCNs) are not robust and inherently water unstable if theTOCNs are not crosslinked or coated with a water-swellable polymer. Furthermore, the manufacturing of self-standing TOCNfilms is still a challenge due to the small TOCN diameter and viscosifying effect. Here, we report the TEMPO-mediatedoxidation of bacterial cellulose (BC) nanopaper as a route to produce robust and water stable TOCN hydrogel without theneed for additional additives or crosslinking steps, as well as self-standing TOCN films without the need for vacuum filtrationor slow-drying of TOCN suspension. Pristine BC pellicle was first press-dried into a dried and well-consolidated BC nanopaper,followed by TEMPO-oxidation at various NaClO concentrations. The oxidation reaction introduced carboxylate moieties ontoexposed BC nanofibrils within the nanopaper network structure. This then led to the swelling of the nanopaper into ahydrogel. A swelling ratio of up to 100 times the original thickness of BC nanopaper was observed upon TEMPO-oxidation.The water retention value of the TEMPO-oxidised BC hydrogels was also found to increase with increasing carboxylatecontent. These TEMPO-oxidised BC hydrogels were found to be robust and water-stable, even under prolonged (>1 month)magnetic stirring in water. We further showed that high grammage self-standing TOCN films (100 g m-2) can be fabricatedas simple as press-drying a water stable TEMPO-oxidised BC hydrogels without the need of vacuum-assisted filtration orslow-drying, which is typically the rate-limiting step in the manufacturing of self-standing TOCN films.

Journal article

Caro-Astorga J, Walker KT, Herrera N, Lee K-Y, Ellis Tet al., 2021, Bacterial cellulose spheroids as building blocks for 3D and patterned living materials and for regeneration., Nature Communications, Vol: 12, Pages: 1-9, ISSN: 2041-1723

Engineered living materials (ELMs) based on bacterial cellulose (BC) offer a promising avenue for cheap-to-produce materials that can be programmed with genetically encoded functionalities. Here we explore how ELMs can be fabricated in a modular fashion from millimetre-scale biofilm spheroids grown from shaking cultures of Komagataeibacter rhaeticus. Here we define a reproducible protocol to produce BC spheroids with the high yield bacterial cellulose producer K. rhaeticus and demonstrate for the first time their potential for their use as building blocks to grow ELMs in 3D shapes. Using genetically engineered K. rhaeticus, we produce functionalized BC spheroids and use these to make and grow patterned BC-based ELMs that signal within a material and can sense and report on chemical inputs. We also investigate the use of BC spheroids as a method to regenerate damaged BC materials and as a way to fuse together smaller material sections of cellulose and synthetic materials into a larger piece. This work improves our understanding of BC spheroid formation and showcases their great potential for fabricating, patterning and repairing ELMs based on the promising biomaterial of bacterial cellulose.

Journal article

Kontturi KS, Lee K-Y, Jones MP, Sampson WW, Bismarck A, Kontturi Eet al., 2021, Influence of biological origin on the tensile properties of cellulose nanopapers, CELLULOSE, Vol: 28, Pages: 6619-6628, ISSN: 0969-0239

Journal article

Gaduan AN, Solhi L, Kontturi E, Lee K-Yet al., 2021, From micro to nano: polypropylene composites reinforced with TEMPO-oxidised cellulose of different fibre widths, CELLULOSE, Vol: 28, Pages: 2947-2963, ISSN: 0969-0239

Journal article

Santmarti A, Tammelin T, Lee K-Y, 2020, Prevention of interfibril hornification by replacing water in nanocellulose gel with low molecular weight liquid poly(ethylene glycol), Carbohydrate Polymers, Vol: 250, Pages: 1-9, ISSN: 0144-8617

Nanocellulose is typically stored and transported as a gel with a nominal solid content of up to 5 wt.-% to avoid interfibril hornification, i.e. the formation of irreversible hydrogen bonds between adjacent nanocellulose upon drying, which makes nanocellulose not cost-effective. In this work, we report the use of low molecular weight liquid poly(ethylene glycol) (PEG-200) as a replacement for the water phase in nanocellulose aqueous gel. Our results indicated that nanocellulose can be stored in PEG-200 at a solid content of up to 70 wt.-% without interfibril hornification, even when exposed to the ambient environment. This is due to the low vapour pressure and high boiling point of PEG-200. ATR-FTIR and ζ-potential measurements confirmed that PEG-200 can be easily washed out from the nanocellulose as PEG-200 is water miscible. Using PEG-200 as a replacement for the water phase in nanocellulose aqueous gel could improve the cost-efficiency of nanocellulose storage and transportation. The tensile properties of the cellulose nanopaper prepared from the various never-dried and once-dried nanocellulose are also discussed in this work.

Journal article

Vilchez V, Dieckmann E, Tammelin T, Cheeseman C, Lee K-Yet al., 2020, Upcycling Poultry Feathers with (Nano)cellulose: Sustainable Composites Derived from Nonwoven Whole Feather Preforms, ACS Sustainable Chemistry & Engineering, Vol: 8, Pages: 14263-14267, ISSN: 2168-0485

Journal article

Santmarti A, Liu HW, Herrera N, Lee K-Yet al., 2020, Anomalous tensile response of bacterial cellulose nanopaper at intermediate strain rates, Scientific Reports, Vol: 10, ISSN: 2045-2322

Nanocellulose network in the form of cellulose nanopaper is an important material structure and its time-dependent mechanical response is crucial in many of its potential applications. In this work, we report the influences of grammage and strain rate on the tensile response of bacterial cellulose (BC) nanopaper. BC nanopaper with grammages of 20, 40, 60 and 80 g m−2 were tested in tension at strain rates ranging from 0.1% s−1 to 50% s−1. At strain rates ≤ 2.5% s−1, both the tensile modulus and strength of the BC nanopapers stayed constant at ~ 14 GPa and ~ 120 MPa, respectively. At higher strain rates of 25% s−1 and 50% s−1 however, the tensile properties of the BC nanopapers decreased significantly. This observed anomalous tensile response of BC nanopaper is attributed to inertial effect, in which some of the curled BC nanofibres within the nanopaper structure do not have enough time to uncurl before failure at such high strain rates. Our measurements further showed that BC nanopaper showed little deformation under creep, with a secondary creep rate of only ~ 10–6 s−1. This stems from the highly crystalline nature of BC, as well as the large number of contact or physical crosslinking points between adjacent BC nanofibres, further reducing the mobility of the BC nanofibres in the nanopaper structure.

Journal article

Song W, Magid A, Li D, Lee K-Yet al., 2020, Application of recycled carbon-fibre-reinforced polymers as reinforcement for epoxy foams., J Environ Manage, Vol: 269

The ever-increasing demand for carbon fibre reinforced polymers (CFRP) and stringent environmental legislation have driven the research into recycling and reusing the CFRP waste. This paper presents a mechanical recycling process of CFRP and the application of the recyclates as reinforcement for epoxy foams. The CFRP was mechanically processed using a jet mill. Up to 10 wt% of the CFRP recyclates, without separation of fibre-rich portion and resin-rich portion, was added into epoxy foams. The compressive modulus and strength of the epoxy foams increased from 288 MPa and 7.0 MPa, respectively, to 1060 MPa and 22.8 MPa, respectively, accompanied with an increase in foam density from 0.37 g cm-3 to 0.68 g cm-3. Consequently, the specific compressive modulus and strength (normalised against density) increased from 789 MPa cm3 g-1 and 19.1 MPa cm3 g-1 for unreinforced foam to 1563 MPa cm3 g-1 and 33.5 MPa cm3 g-1 for CFRP recyclates reinforced foam, representing a 98% and 75% improvement, respectively. These results demonstrate that the CFRP recyclates have excellent reinforcing ability for epoxy foams.

Journal article

Gregory GL, Sulley GS, Carrodeguas LP, Chen TTD, Santmarti A, Terrill NJ, Lee K-Y, Williams CKet al., 2020, Triblock polyester thermoplastic elastomers with semi-aromatic polymer end blocks by ring-opening copolymerization, Chemical Science, Vol: 11, Pages: 6567-6581, ISSN: 2041-6520

Thermoplastic elastomers benefit from high elasticity and straightforward (re)processability; they are widely used across a multitude of sectors. Currently, the majority derive from oil, do not degrade or undergo chemical recycling. Here a new series of ABA triblock polyesters are synthesized and show high-performances as degradable thermoplastic elastomers; their composition is poly(cyclohexene-alt-phthalate)-b-poly(ε-decalactone)-b-poly(cyclohexene-alt-phthalate) {PE–PDL–PE}. The synthesis is accomplished using a zinc(II)/magnesium(II) catalyst, in a one-pot procedure where ε-decalactone ring-opening polymerization yielding dihydroxyl telechelic poly(ε-decalatone) (PDL, soft-block) occurs first and, then, addition of phthalic anhydride/cyclohexene oxide ring-opening copolymerization delivers semi-aromatic polyester (PE, hard-block) end-blocks. The block compositions are straightforward to control, from the initial monomer stoichiometry, and conversions are high (85–98%). Two series of polyesters are prepared: (1) TBPE-1 to TBPE-5 feature an equivalent hard-block volume fraction (fhard = 0.4) and variable molar masses 40–100 kg mol−1; (2) TBPE-5 to TBPE-9 feature equivalent molar masses (∼100 kg mol−1) and variable hard-block volume fractions (0.12 < fhard < 0.4). Polymers are characterized using spectroscopies, size-exclusion chromatography (SEC), thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA). They are amorphous, with two glass transition temperatures (∼−51 °C for PDL; +138 °C for PE), and block phase separation is confirmed using small angle X-ray scattering (SAXS). Tensile mechanical performances reveal thermoplastic elastomers (fhard < 0.4 and N > 1300) with linear stress–strain relationships, high ultimate tensile strengths (σb = 1–5 MPa), very high elongations at break (&ep

Journal article

Mautner A, Nawawi WMFW, Lee K-Y, Bismarck Aet al., 2020, High porosity cellulose nanopapers as reinforcement in multi-layer epoxy laminates, Composites Part A: Applied Science and Manufacturing, Vol: 131, Pages: 1-9, ISSN: 1359-835X

Utilizing high-performance cellulose nanopapers as 2D-reinforcement for polymers allows for realizing high-loading-fraction (80 vol-%), high-performance (strength > 150 MPa, modulus > 10 GPa) laminated nanopaper reinforced epoxy composites. Such cellulose nanopapers are inherently dense, which renders them difficult to be impregnated with the epoxy-resin. High-porosity nanopapers facilitate better resin impregnation, truly utilizing the properties of single cellulose nanofibres instead of the nanofibre network. We report the use of high-porosity (74%) but low strength and modulus bacterial cellulose (BC) nanopapers, prepared from BC-in-ethanol dispersion, as reinforcement for epoxy-resin. High-porosity nanopapers allowed for full impregnation of the BC-nanopapers with epoxy-resin. The resulting BC-reinforced epoxy-laminates possessed high tensile modulus (9 GPa) and strength (100 MPa) at a BC loading of 30 vol-%, resulting from very low void-fraction (3 vol-%) of these papregs compared to conventional nanopaper-laminates (10+ vol.-%). Better resin impregnation of less dense nanocellulose networks allowed for maximum utilization of stiffness/strength of cellulose nanofibrils.

Journal article

Nawawi WMFW, Lee K-Y, Kontturi E, Bismarck A, Mautner Aet al., 2020, Surface properties of chitin-glucan nanopapers from Agaricus bisporus, International Journal of Biological Macromolecules, Vol: 148, Pages: 677-687, ISSN: 0141-8130

The structural component of fungal cell walls comprises of chitin covalently bonded to glucan; this constitutes a native composite material (chitin-glucan, CG) combining the strength of chitin and the toughness of glucan. It has a native nano-fibrous structure in contrast to nanocellulose, for which further nanofibrillation is required. Nanopapers can be manufactured from fungal chitin nanofibrils (FChNFs). FChNF nanopapers are potentially applicable in packaging films, composites, or membranes for water treatment due to their distinct surface properties inherited from the composition of chitin and glucan. Here, chitin-glucan nanofibrils were extracted from common mushroom (Agaricus bisporus) cell walls utilizing a mild isolation procedure to preserve the native quality of the chitin-glucan complex. These extracts were readily disintegrated into nanofibre dimensions by a low-energy mechanical blending, thus making the extract dispersion directly suitable for nanopaper preparation using a simple vacuum filtration process. Chitin-glucan nanopaper morphology, mechanical, chemical, and surface properties were studied and compared to chitin nanopapers of crustacean (Cancer pagurus) origin. It was found that fungal extract nanopapers had distinct physico-chemical surface properties, being more hydrophobic than crustacean chitin.

Journal article

Sulley GS, Gregory GL, Chen TTD, Carrodeguas LP, Trott G, Santmarti A, Lee K-Y, Terrill NJ, Williams CKet al., 2020, Switchable catalysis improves the properties of CO2-derived polymers: poly(cyclohexene carbonate-b-epsilon-decalactone-b-cyclohexene carbonate) adhesives, elastomers, and toughened plastics, Journal of the American Chemical Society, Vol: 142, Pages: 4367-4378, ISSN: 0002-7863

Carbon dioxide/epoxide copolymerization is an efficient way to add value to waste CO2 and to reduce pollution in polymer manufacturing. Using this process to make low molar mass polycarbonate polyols is a commercially relevant route to new thermosets and polyurethanes. In contrast, high molar mass polycarbonates, produced from CO2, generally under-deliver in terms of properties, and one of the most widely investigated, poly(cyclohexene carbonate), is limited by its low elongation at break and high brittleness. Here, a new catalytic polymerization process is reported that selectively and efficiently yields degradable ABA-block polymers, incorporating 6–23 wt % CO2. The polymers are synthesized using a new, highly active organometallic heterodinuclear Zn(II)/Mg(II) catalyst applied in a one-pot procedure together with biobased ε-decalactone, cyclohexene oxide, and carbon dioxide to make a series of poly(cyclohexene carbonate-b-decalactone-b-cyclohexene carbonate) [PCHC-PDL-PCHC]. The process is highly selective (CO2 selectivity >99% of theoretical value), allows for high monomer conversions (>90%), and yields polymers with predictable compositions, molar mass (from 38–71 kg mol–1), and forms dihydroxyl telechelic chains. These new materials improve upon the properties of poly(cyclohexene carbonate) and, specifically, they show good thermal stability (Td,5 ∼ 280 °C), high toughness (112 MJ m–3), and very high elongation at break (>900%). Materials properties are improved by precisely controlling both the quantity and location of carbon dioxide in the polymer chain. Preliminary studies show that polymers are stable in aqueous environments at room temperature over months, but they are rapidly degraded upon gentle heating in an acidic environment (60 °C, toluene, p-toluene sulfonic acid). The process is likely generally applicable to many other lactones, lactides, anhydrides, epoxides, and heterocumulenes and sets the s

Journal article

Santmarti A, Zhang H, Lappalainen T, Lee K-Yet al., 2020, Cellulose nanocomposites reinforced with bacterial cellulose sheets prepared from pristine and disintegrated pellicle, Composites Part A: Applied Science and Manufacturing, Vol: 130, Pages: 1-9, ISSN: 1359-835X

BC sheets can be prepared in two forms: direct press-drying of the as-synthesised BC pellicle or disintegrating the BC pellicle to create a homogenous BC-in-water suspension prior to producing the BC sheet. We found that BC sheet prepared from direct press-drying of pristine pellicle was more homogeneous due to its better BC network formation and possessed higher specific surface area (46 g m−2), better resin impregnation and mechanical properties compared to its disintegrated pellicle counterpart (21 g m−2). BC-poly(acrylated epoxidised soybean oil) (polyAESO) nanocomposites consisting of BC sheet prepared from pristine pellicle was optically transparent whilst BC-polyAEO nanocomposites consisting of BC sheet prepared from disintegrated pellicle was opaque. Whilst the tensile properties of BC-polyAESO nanocomposites from pristine pellicle were higher, the fracture toughness of BC-polyAESO composite consisting of BC sheet from disintegrated pellicle was better. The lack of resin impregnation in BC-polyAESO from disintegrated pellicle led to a laminated structure, which utilised the fracture toughness of BC sheet effectively.

Journal article

Nawawi WMFBW, Jones M, Murphy RJ, Lee K-Y, Kontturi E, Bismarck Aet al., 2020, Nanomaterials derived from fungal sources-is It the new hype?, Biomacromolecules, Vol: 21, Pages: 30-55, ISSN: 1525-7797

Greener alternatives to synthetic polymers are constantly being investigated and sought after. Chitin is a natural polysaccharide that gives structural support to crustacean shells, insect exoskeletons, and fungal cell walls. Like cellulose, chitin resides in nanosized structural elements that can be isolated as nanofibers and nanocrystals by various top-down approaches, targeted at disintegrating the native construct. Chitin has, however, been largely overshadowed by cellulose when discussing the materials aspects of the nanosized components. This Perspective presents a thorough overview of chitin-related materials research with an analytical focus on nanocomposites and nanopapers. The red line running through the text emphasizes the use of fungal chitin that represents several advantages over the more popular crustacean sources, particularly in terms of nanofiber isolation from the native matrix. In addition, many β-glucans are preserved in chitin upon its isolation from the fungal matrix, enabling new horizons for various engineering solutions.

Journal article

Jiang Q, Lee K, Bismarck A, 2020, Foam templating: A greener route to porous polymers, ACS Symposium Series, Pages: 99-118

A simple kitchen mixer and skills to whip cream can be useful to manufacture highly functional polymer foams with control over their structures. In the 1930s, researchers began to whip or inject gas into monomers or polymer suspensions to produce liquid foams, which served as templates to be solidified to polymer foams. Besides the “simplicity” of the foam templating method, its actual advantage as compared to widely used blown polymer foams is the nonessential need of physical and chemical blowing agents, resulting in a lower raw material cost, less involved chemistry, lower safety and health risk during production and a reduced impact on the environment. Compared to other templating methods, such as emulsion templating, which require sacrificial materials serving as templates, liquid foams with bubbles as templates are superior from a material processing perspective because they require no further materials or energy for template removal. A challenging step in foam templating is to create a stable liquid foam containing building blocks for subsequent solidification; when using air as an internal phase, the choice of materials in the liquid phase to create a stable colloidal system is restricted. In this chapter, we review previous work on foam templating with a focus on porous materials produced therefrom, including macroporous thermoplastic, thermosetting polymers, hydrogels, biobased materials and polymer composites. We aim to show that foam templating is a greener than any other templating methods, such as emulsion templating and particulate leaching, and versatile foaming process and to encourage researchers to conduct both fundamental and applied research to push the boundaries of this technology further.

Book chapter

Song W, Konstantellos G, Li D, Lee K-Yet al., 2019, Short carbon fibre-reinforced epoxy foams with isotropic cellular structure and anisotropic mechanical response produced from liquid foam templates, Composites Science and Technology, Vol: 184, Pages: 1-9, ISSN: 0266-3538

In this work, we show that mechanically anisotropic short carbon fibre (sCF)-reinforced epoxy foams with an isotropic cellular structure can be fabricated from liquid foam templates. Short carbon fibres were mechanically frothed in an uncured liquid epoxy resin to produce an air-in-resin liquid foam template, followed by subsequent polymerisation. Fracture toughness test showed that the incorporation of short carbon fibres into the epoxy foams led to a significant increase in their critical stress intensity factors. It was also observed that neat epoxy foams failed catastrophically whilst sCF-reinforced epoxy foams failed in a progressive manner. Compression test further showed that the in-plane compressive moduli of the mechanically frothed sCF-reinforced epoxy foams were significantly higher than their out-of-plane compressive moduli, signifying an anisotropic mechanical response. This anisotropic mechanical response stemmed from the radial flow generated by the high intensity mechanical frothing process, facilitating the preferential orientation of the added short carbon fibres in-plane whilst the entrained air bubbles during the mechanical frothing process were in equilibrium with the surrounding uncured liquid epoxy resin, resulting in an epoxy foam with an isotropic (spherical) cellular structure.

Journal article

Mishnaevsky L, Mikkelsen LP, Gaduan AN, Lee KY, Madsen Bet al., 2019, Nanocellulose reinforced polymer composites: Computational analysis of structure-mechanical properties relationships, Composite Structures, Vol: 224, ISSN: 0263-8223

Structure-mechanical properties relationships of nanocellulose reinforced polymer composites are studied in computational experiments. A code for the generation of 3D unit cell finite element models of nanocellulose reinforced polymers with “snake”-shaped nanocellulose fibrils is developed. The code allows the generation of pre-defined nanocomposites structures, with varied angles between nanocellulose snakes segments and hydrogen bonds between nanocellulose fibrils. In a series of computational studies, it is demonstrated that the nanocellulose reinforcement leads to higher stiffness of the matrix polymer, but makes it more brittle.

Journal article

Suwan K, Waramit S, Przystal J, Stoneham C, Bentayebi K, Asavarut P, Chongchai A, Pothachareon P, Lee K-Y, Topanurak S, Smith T, Gelovani J, Sidman R, Pasqualini R, Arap W, Hajitou Aet al., 2019, Next-generation of targeted AAVP vectors for systemic transgene delivery against cancer, Proceedings of the National Academy of Sciences of USA, Vol: 116, Pages: 18571-18577, ISSN: 0027-8424

Bacteriophage (phage) have attractive advantages as delivery sys-tems compared to mammalian viruses, but have been consideredpoor vectors because they lack evolved strategies to confrontand overcome mammalian cell barriers to infective agents. Wereasoned that improved efficacy of delivery might be achievedthrough structural modification of the viral capsid to avoid pre-and post-internalization barriers to mammalian cell transduction.We generated multifunctional hybrid AAV/phage (AAVP) particlesto enable simultaneous display of targeting ligands on the phage’sminor pIII proteins and also degradation-resistance motifs on thevery numerous pVIII coat proteins. This genetic strategy of directedevolution, bestows a next-generation of AAVP particles that fea-ture resistance to fibrinogen adsorption or neutralizing antibodies,and ability to escape endolysosomal degradation. This results insuperior gene transfer efficacyin vitroand also in preclinicalmouse models of rodent and human solid tumors. Thus, the uniquefunctions of our next-generation AAVP particles enable improvedtargeted gene delivery to tumor cells.

Journal article

Karim Z, Svedberg A, Lee K-Y, Khan MJet al., 2019, Processing-atructure-property correlation understanding of microfibrillated cellulose based dimensional structures for ferric ions removal, Scientific Reports, Vol: 9, Pages: 1-12, ISSN: 2045-2322

In this research article, wood based microfibrillated cellulose (MFC) was studied to gain a better understanding of the process of dependent network formation. Networking potential and obtained properties of the produced dimensional structures could be controlled using opted processing routes. The fabricated dimensional structure, using freeze-drying (FD) is a highly open and porous network (98% porosity) compared to slightly tight, dense and less porous network produced after pressing at 200kN (96% porosity), followed by vacuum-filtered (VF) networks (33% porosity). The porosity (17%) was further decreased when the casting (CS) method was used, further producing a highly dense and compressed network. High water flux (180.8 ± 11 L/m2h) of pressed freeze-dried (PFD) followed by vacuum-filtered (VF) (11.4 ± 1.9 L/m2h) and casting CS (0.7 ± 0.01 L/m2h) were calculated using device. Furthermore, increased water flux (1.4 fold) of Experimental Paper Machine (XPM) based structures was reported in comparison with CS structures. Pore-sized distribution and surface area were measured using Hg porosimetry; they showed an average pore size of 16.5 μm for FD, followed by PFD (8.2 μm) structures. A 27-fold decrease in average pore-size was observed for CS structure in comparison with the FD structures. Highest tensile strength (87 ± 21 MPa) was recorded for CS structures, indicating a more highly compacted network formation compared to VF (82 ± 19 MPa) and PFD (1.6 ± 0.06 MPa). Furthermore, an attempt was made to upscale the VF structures using traditional paper making approach on XMP. Improved tensile strength (73 ± 11 MPa) in machine produced structures is due to alignment of fibers towards machine direction compared to cross directional (43 ± 9 MPa)

Journal article

Dieckmann E, Eleftheriou K, Audic T, Lee KY, Sheldrick L, Cheeseman Cet al., 2019, New sustainable materials from waste feathers: Properties of hot-pressed feather/cotton/bi-component fibre boards, Sustainable Materials and Technologies, Vol: 20, ISSN: 2214-9937

Feathers from poultry are an abundant, globally available waste. The current beneficial reuse for feathers involves autoclaving them to produce feather meal, an animal feed with low economic value. This paper reports on the production and performance of new feather-derived materials. These have potential to provide a higher value application for waste feathers. Feather fibres, cotton fibres and polyethylene/polypropylene bi-component fibres (blended 55:20:25 by weight) have been air-laid to form 20 mm thick non-woven pre-forms with a density of 0.14 g cm −2 . These were then hot pressed to produce materials with significantly higher density and improved properties. Optimum materials were formed by hot pressing between 150 and 160 °C at 6 MPa for 1 min. Lower temperatures resulted in poor fibre bonding and fibre pull-out during fracture. Higher temperatures caused thermal degradation of the feather fibres. The optimum feather fibre boards with a density of 0.77 g/cm 3 , corresponding to 31.3% porosity, had tensile strengths of 17.9 MPa a tensile modulus of 1.74 GPa and an elongation at fracture of 5.9%. These samples exhibited fibre fracture during tensile testing. Feather fibre boards have similar tensile strength, density and Young's modulus to particleboard, organic resin particleboard and flake board. Quantitative estimates of the economic and environmental benefits from using feather fibres to form feather fibre boards are discussed. The research advances sustainability by providing a new potential circular economy outlet for waste feathers and is part of on-going research to develop novel applications that exploit the unique properties of feathers.

Journal article

Santmarti A, Teh JW, Lee K-Y, 2019, Transparent poly(methyl methacrylate) composites based on bacterial cellulose nanofibre networks with improved fracture resistance and impact strength, ACS Omega, Vol: 4, Pages: 9896-9903, ISSN: 2470-1343

Cellulose nanofibers are often explored as biobased reinforcement for the production of high-performance composite materials. In this work, we fabricated transparent poly(methyl methacrylate) (PMMA) composites consisting of two-dimensional and three-dimensional bacterial cellulose (BC) nanofiber networks. Three different composite designs consisting of 1 vol % BC loading were fabricated and studied: (i) composites with a three-dimensional BC nanofiber network embedded uniformly throughout the PMMA matrix; (ii) sandwich-structured construction consisting of three-dimensional BC–PMMA sandwiched between two neat PMMA sheets; and (iii) dried and well-consolidated two-dimensional BC nanofiber network embedded in a PMMA matrix. All fabricated model BC–PMMA composites were found to be optically transparent, but PMMA composites consisting of the two-dimensional BC nanofiber network possessed higher light transmittance (73% @550 nm) compared to the three-dimensional BC nanofiber network counterparts (63% @550 nm). This is due to the higher specific surface area of the three-dimensional BC nanofiber network, which led to more light scattering. Nevertheless, it was found that both two-dimensional and three-dimensional BC nanofiber networks serve as excellent stiffening agents for PMMA matrix, improving the tensile modulus of the resulting composites by up to 30%. However, no improvement in tensile strength was observed. The use of three-dimensional BC nanofiber network led to matrix embrittlement, reducing the tensile strain-at-failure, fracture resistance, and Charpy impact strength of the resulting BC–PMMA composites. When the BC nanofiber network was used as two-dimensional reinforcement, cracks were observed to propagate through the debonding of BC nanofiber network, leading to higher fracture toughness and Charpy impact strength. These novel findings could open up further opportunities in the design of novel optically transparent polymeric composite lami

Journal article

Fazli Wan Nawawi WM, Lee KY, Kontturi E, Murphy RJ, Bismarck Aet al., 2019, Chitin nanopaper from mushroom extract: natural composite of nanofibers and glucan from a single biobased source, ACS Sustainable Chemistry and Engineering, Vol: 7, Pages: 6492-6496, ISSN: 2168-0485

An isolation method with mild mechanical agitation and no acidic extraction step from a mushroom substrate resulted in chitin nanofibers (ChNFs) with large shares of retained glucans (50-65%). The subsequent chitin nanopapers exhibited exceptionally high tensile strengths of >200 MPa and moduli of ca. 7 GPa, which were largely attributed to the preserved glucans in the mixture, imparting a composite nature to the nanopapers. The isolation method for ChNFs is notably different from the conventional process with crustacean chitin sources that do not incorporate glucans and where an acidic extraction step for the removal of minerals must always be included.

Journal article

Mohammed C, Mahabir S, Mohammed K, John N, Lee K-Y, Ward Ket al., 2019, Calcium Alginate Thin Films Derived from Sargassum natans for the Selective Adsorption of Cd2+, Cu2+, and Pb2+ Ions, Industrial & Engineering Chemistry Research, Vol: 58, Pages: 1417-1425, ISSN: 0888-5885

The Caribbean has seen the influx of Sargassum, affecting the livelihood of communities. Sodium alginate extracted from Sargassum is known for its cross-linking properties, making the seaweed attractive as an adsorbent. Hence, the use of calcium alginate thin films can decrease the mass transfer resistance found in commonly used alginate beads, resulting in increased adsorption efficiency. This Article discusses the potential of calcium alginate thin films for Pb2+, Cu2+, and Cd2+ ion adsorption. Pb2+, Cu2+, and Cd2+ adsorption fitted the Langmuir isotherm well with capacities of 0.80, 0.10, and 0.02 mmol of metal/g, respectively, for Sargassum. Kinetic studies showed that the ions followed the pseudo-second-order model, elucidating that ion exchange governed adsorption. Furthermore, NMR characterization showed that G-block monomers influenced kinetic parameters and selectivity in the following order: Pb2+ > Cu2+ > Cd2+

Journal article

Chen G, Lee K-Y, Bismarck A, Li Ret al., 2019, Cellulose materials and methods of making and using same, US10,988,897

Patent

Song W, Tagarielli VL, Lee KY, 2018, Enhancing the fracture resistance and impact toughness of mechanically frothed epoxy foams with hollow elastomeric microspheres, Macromolecular Materials and Engineering, Vol: 303, ISSN: 1438-7492

Nonporous elastomeric particles are often employed to improve the toughness of brittle epoxy foams but this also decreases their compressive strength and stiffness. Herein, a novel strategy utilizing hollow elastomeric microspheres as toughening agent for epoxy foams is presented. The addition of 0.5 wt.% hollow elastomeric microspheres into epoxy foam leads to a 15% increase in critical stress intensity factor (K1c) to 0.38 MPa m0.5and 33% increase in Charpy impact strength (acU) to 1.05 kJ m−2, respectively, compared to unfilled epoxy foam (K1c = 0.33 MPa m0.5and acU= 0.79 kJ m−2). However, a further increase in the hollow elastomeric microsphere concentration to 1.0 wt.% leads to microsphere agglomeration, which reduces both K1cand acUto 0.35 MPa m0.5and 0.93 kJ m−2, respectively. Nevertheless, the added hollow elastomeric microspheres do not lead to a reduction in the quasi-static compressive properties of the epoxy foams.

Journal article

Hervy M, Bock F, Lee KY, 2018, Thinner and better: (Ultra-)low grammage bacterial cellulose nanopaper-reinforced polylactide composite laminates, Composites Science and Technology, Vol: 167, Pages: 126-133, ISSN: 0266-3538

One of the rate-limiting steps in the large-scale production of cellulose nanopaper-reinforced polymer composites is the time consuming dewatering step to produce the reinforcing cellulose nanopapers. In this work, we show that the dewatering time of bacterial cellulose (BC)-in-water suspension can be reduced by reducing the grammage of BC nanopaper to be produced. The influence of BC nanopaper grammage on the tensile properties of BC nanopaper-reinforced polylactide (PLLA) composites is also investigated in this work. BC nanopaper with grammages of 5, 10, 25 and 50 g m−2 were produced and it was found that reducing the grammage of BC nanopaper from 50 g m−2 to 5 g m−2 led to a three-fold reduction in the dewatering time of BC-in-water suspension. The porosity of the BC nanopapers, however, increased with decreasing BC nanopaper grammage. While the tensile properties of BC nanopapers were found to decrease with decreasing BC nanopaper grammage, no significant difference in the reinforcing ability of BC nanopaper with different grammages for PLLA was observed. All PLLA composite laminates reinforced with BC nanopapers possessed similar tensile modulus of 10.5–11.8 GPa and tensile strength of 95–111 MPa, respectively, at a BC loading fraction  = 39–53 vol.-%, independent of the grammage and tensile properties of the reinforcing BC nanopaper.

Journal article

Mohammed A, Bissoon R, Bajnath E, Mohammed K, Lee T, Bissram M, John N, Jalsa NK, Lee KY, Ward Ket al., 2018, Multistage extraction and purification of waste Sargassum natans to produce sodium alginate: an optimization approach, Carbohydrate Polymers, Vol: 198, Pages: 109-118, ISSN: 0144-8617

Sargassum in the Caribbean region has affected the livelihood of several coastal communities due to the influx of large quantities of the seaweed in recent times. This article seeks to explore how waste Sargassum natans can be utilized to produce sodium alginate. The novelty in this research lies in the optimization process, whereby multistage extraction and precipitation were investigated over commonly used single stage processing, in an effort to maximize both yield and purity. The results showed that a maximum yield of 19% was observed after 1 stage, while the purity was 74% after 4 stages. In addition, optimization of the multistage precipitation process using the Global Optimization Toolbox in MATLAB R2017b provided a novel model which indicated that a compromise between the maximum purity and yield can be obtained at 3 stages; 71–74% and 12–16% respectively. Furthermore, characterization was done using FTIR and NMR, with results comparable to a commercial sodium alginate brand, giving absorption bands at 1610 cm−1and 1395 cm-1and an M/G ratio of 0.51 respectively.

Journal article

Narducci F, Lee K, Pinho ST, 2018, Realising damage-tolerant nacre-inspired CFRP, Journal of the Mechanics and Physics of Solids, Vol: 116, Pages: 391-402, ISSN: 0022-5096

Inthiswork,anacre-inspiredCarbonFibreReinforcedPolymer(CFRP)compositeis designed,synthesisedandtested. Analyticalandnumericalmodelsareusedtodesign a tiled micro-structure, mimicking the staggered arrangement of ceramic platelets in nacreandexploitinggeometricalinterlocksforcrackdeflectionanddamagediffusion. The designed pattern of tiles is then laser-engraved in the laminate plies. In order to increase the damage-spreading capability of the material, a thin layer of poly(lactic acid) (PLA) is film-cast on the interlaminar region, both as a continuous film and as a pattern of fractal-shaped patches. Three-point bending tests show how the nacre-like micro-structure succeeds in deflecting cracks, with damage diffusion being significantly improved by the addition of PLA at the interface between tiles. It is observed that a texture of discontinuous fractal-shaped PLA patches can increase damage diffusion, by promoting the unlocking of tiles whilst preserving the interface strength.

Journal article

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