Original Macromolecular Architectures Based on poly(ε-caprolactone) and poly(ε-thiocaprolactone) Grafted onto Chitosan Backbone

Polyester and/or polythioester grafted chitosan copolymers were synthesized. For that, poly(ε-caprolactone) (PCL), poly(ε-thiocaprolactone) (PTCL), and their copolymers were first synthesized by ring opening polymerization. Copolymers with caprolactone:thiocaprolactone (CL:TCL) molar ratios of 2:1, 1:1, 1:2 were synthesized. All of the synthesized macromolecular architectures were characterized using different spectral (Fourier transform infrared (FTIR), proton nuclear magnetic resonance (1H-NMR), X-Ray diffraction (XRD)) and thermal (Differential scanning calorimetry (DSC), Thermogravimetric analysis (TGA)) methods. Grafting was then performed according two distinct routes: (i) using a blend of both homopolymers (PCL and PTCL) or (ii) using pre-synthesized copolymers with controlled CL:TCL ratios. Hexamethylene diisocyanate was used as a grafting/coupling agent through urethane bonds with high yield. Grafting preferentially occurred at sulfur sites. The results indicated that PTCL is more reactive and favorable than PCL for grafting onto chitosan. With the homopolymers blend grafting route, the corresponding materials mostly had a higher PTCL portion than expected. To obtain polyester grafted chitosan with a determined CL:TCL ratio, the copolymer grafting route would yield better result

Effect of crystallization on barrier properties of formulated polylactide

Polylactide (PLA), a biodegradable polymer obtained from biomass, was formulated with a nucleating agent, talc, and a plasticizer, acetyl tributyl citrate, and cold crystallized in α and α′ form. The barrier properties of crystallized PLA were investigated as a function of the formulation and the crystalline form, thanks to three molecules with increasing polymer interactions, i.e. helium, oxygen and ethyl acetate (EA). Contrary to expectation, the oxygen diffusion coefficient in neat and formulated PLA did not decrease with crystallization. Even an increase of the diffusion coefficient was noticed for the most interacting probe, EA, in formulated PLA. Conditioning of neat and formulated PLA in an atmosphere containing EA vapour caused a modification of the material structure by plasticization and induced crystallization even at small EA activities. The plasticizing effect caused the glass transition temperature Tg to shift to below ambient temperature. In the case of neat PLA induced crystallization in solely the α form was obtained, and in the case of formulated PLA a blend of α and α′ forms was observed. Copyright © 2011 Society of Chemical Industr

Effect of crystallization on barrier properties of formulated polylactide

Polylactide (PLA), a biodegradable polymer obtained from biomass, was formulated with a nucleating agent, talc, and a plasticizer, acetyl tributyl citrate, and cold crystallized in α and α′ form. The barrier properties of crystallized PLA were investigated as a function of the formulation and the crystalline form, thanks to three molecules with increasing polymer interactions, i.e. helium, oxygen and ethyl acetate (EA). Contrary to expectation, the oxygen diffusion coefficient in neat and formulated PLA did not decrease with crystallization. Even an increase of the diffusion coefficient was noticed for the most interacting probe, EA, in formulated PLA. Conditioning of neat and formulated PLA in an atmosphere containing EA vapour caused a modification of the material structure by plasticization and induced crystallization even at small EA activities. The plasticizing effect caused the glass transition temperature Tg to shift to below ambient temperature. In the case of neat PLA induced crystallization in solely the α form was obtained, and in the case of formulated PLA a blend of α and α′ forms was observed. Copyright © 2011 Society of Chemical Industr

Study and characterisation of the post processing ageing of sago pith waste biocomposites

This paper reports the post-processing ageing phenomena of thermoplastic sago starch (TPS) and plasticised sago pith waste (SPW), which were processed using twin-screw extrusion and compression moulding techniques. Wide angle X-ray diffraction (XRD) analyses showed that after processing, starch molecules rearranged into VH-type (which was formed rapidly right post processing and concluded within 4 days) and B-type (which was formed slowly over a period of months) crystallites. Evidence from Fourier transform infrared spectroscopy (FTIR) analyses corroborated the 2-stage crystallisation process, which observed changes in peak styles and peak intensities (at 1043 and 1026 cm-1) and band-narrowing. Thermogravimetric analysis (TGA) studies showed that the thermal stability of plasticised SPW declined continuously for 90 days before gradual increments ensued. For all formulations tested, post-processing ageing led to drastic changes in the tensile strength (increased) and elongation at break (decreased). Glycerol and fibres restrained the retrogradation of starch molecules in TPS and SPW

Production and characterization of two medium-chain-length polydroxyalkanoates by engineered strains of Yarrowia lipolytica

Background: The oleaginous yeast Yarrowia lipolytica is an organism of choice for the tailored production of various compounds such as biofuels or biopolymers. When properly engineered, it is capable of producing medium-chain-length polyhydroxyalkanoate (mcl-PHA), a biobased and biodegradable polymer that can be used as bioplastics or biopolymers for environmental and biomedical applications.Results: This study describes the bioproduction and the main properties of two different mcl-PHA polymers. We generated by metabolic engineering, strains of Y. lipolytica capable of accumulating more than 25% (g/g) of mcl-PHA polymers. Depending of the strain genetic background and the culture conditions, we produced (i) a mcl-PHA homopolymer of 3-hydroxydodecanoic acids, with a mass-average molar mass (M-w) of 316,000 g/mol, showing soft thermoplastic properties with potential applications in packaging and (ii) a mcl-PHA copolymer made of 3-hydroxyoctanoic (3HO), decanoic (3HD), dodecanoic (3HDD) and tetradecanoic (3TD) acids with a M-w of 128,000 g/mol, behaving like a thermoplastic elastomer with potential applications in biomedical material.Conclusion: The ability to engineer Y. lipolytica to produce tailored PHAs together with the range of possible applications regarding their biophysical and mechanical properties opens new perspectives in the field of PHA bioproduction

Analysis of the Structure-Properties Relationships of Different Multiphase Systems Based on Plasticized Poly(Lactic Acid)

Poly(lactic acid) is one of the most promising biobased and biodegradable polymers for food packaging, an application which requires good mechanical and barrier properties. In order to improve the mechanical properties, in particular the flexibility, PLA plasticization is required. However, plasticization induces generally a decrease in the barrier properties. Acetyl tributyl citrate (ATBC) and poly(ethylene glycol) 300 (PEG), highly recommended as plasticizers for PLA, were added up to 17 wt% in P(D,L)LA. In the case of PEG, a phase separation was observed for plasticizer contents higher than 5 wt%. Contrary to PEG, the Tg decrease due to ATBC addition, modelled with Fox’s law, and the absence of phase separation, up to 17 wt% of plasticizer, confirm the miscibility of PLA and ATBC. Contents equal or higher than 13 wt% of ATBC yielded a substantial improvement of the elongation at break, becoming higher than 300%. The effect of PLA plasticization on the barrier properties was assessed by different molecules, with increasing interaction with the formulated material, such as helium, an inert gas, and oxygen and water vapour. In comparison to the neat sample, barrier properties against helium were maintained when PLA was plasticized with up to 17 wt% of ATBC. The oxygen permeability coefficient and the water vapour transmission rate doubled for mixtures with 17 wt% ATBC in PLA, but increased five-fold in the PEG plasticized samples. This result is most likely caused by increased solubility of oxygen and water in the PEG phase due to their mutual miscibility. To conclude, ATBC increases efficiently the elongation at break of PLA while maintaining the permeability coefficient of helium and keeping the barrier properties against oxygen and water vapour in the same order of magnitude

Elaboration and properties of plasticised chitosan-based exfoliated nano-biocomposites

A series of plasticised chitosan-based materials and nanocomposites were successfully prepared by thermomechanical kneading. During the processing, the montmorillonite (MMT) platelets were fully delaminated. The nanoclay type and content and the preparation method were seen to have an impact on the crystallinity, morphology, glass transition temperature, and mechanical properties of the samples. When higher content (5%) of MMT–Na+ or either content (2.5% or 5%) of chitosan-organomodified MMT (OMMT–Ch) was used, increases in crystallinity and glass transition temperature were observed. Compared to the neat chitosan, the plasticised chitosan-based nano-biocomposites showed drastically improved mechanical properties, which can be ascribed to the excellent dispersion and exfoliation of nanoclay and the strong affinity between the nanoclay and the chitosan matrix. The best mechanical properties obtained were Young's modulus of 164.3 MPa, tensile strength of 13.9 MPa, elongation at break of 62.1%, and energy at break of 0.671 MPa. While the degree of biodegradation was obviously increased by the presence of glycerol, a further increase might be observed especially by the addition of unmodified nanoclay. This could surprisingly contribute to full (100%) biodegradation after 160 days despite the well-known antimicrobial property of chitosan. The results in this study demonstrate the great potential of plasticised chitosan-based nano-biocomposites in applications such as e.g., biodegradable packaging materials

Alginate-based materials:Enhancing properties through multiphase formulation design and processing innovation

Alginate, a polymer mainly derived from seaweed, has garnered significant attention owing to its renewability, biocompatibility, biodegradability, and exceptional gel formation characteristics, rendering it highly versatile for numerous applications. Recognizing the imperative for tailored bulk materials, this review scrutinizes the processing methodologies of alginate-based bulk materials and delineates strategies to improve their properties, encompassing ionic crosslinking, plasticization, and hybridization with other polymers and/or fillers. It explores noteworthy alginate-based blends with natural polymers like polysaccharides and proteins, alongside fossil-based polymers like poly(vinyl alcohol). It also examines alginate-based composites incorporating various nanofillers such as cellulose nanoparticles, graphene, and nanoclays. The processing techniques for these multiphase alginate-based systems encompass solution casting, coating, spinning, 3D printing, and thermomechanical processing. Strategies for crosslinking alginate, plasticizing it, and optimizing its interactions with other polymers/fillers are outlined, bearing repercussions on the resultant materials properties. This review emphasizes the structure–process–property relationships of these multiphase systems in bulk and highlights synergistic effects and potential impediments to property improvements. It surveys prospective applications for alginate-based multiphasic bulk materials, spanning membrane separation, controlled release, wound healing, tissue engineering, food packaging, and agricultural domains. Finally in this field, knowledge gaps have been identified and future research directions are suggested.</p

Alginate-based materials:Enhancing properties through multiphase formulation design and processing innovation

Alginate, a polymer mainly derived from seaweed, has garnered significant attention owing to its renewability, biocompatibility, biodegradability, and exceptional gel formation characteristics, rendering it highly versatile for numerous applications. Recognizing the imperative for tailored bulk materials, this review scrutinizes the processing methodologies of alginate-based bulk materials and delineates strategies to improve their properties, encompassing ionic crosslinking, plasticization, and hybridization with other polymers and/or fillers. It explores noteworthy alginate-based blends with natural polymers like polysaccharides and proteins, alongside fossil-based polymers like poly(vinyl alcohol). It also examines alginate-based composites incorporating various nanofillers such as cellulose nanoparticles, graphene, and nanoclays. The processing techniques for these multiphase alginate-based systems encompass solution casting, coating, spinning, 3D printing, and thermomechanical processing. Strategies for crosslinking alginate, plasticizing it, and optimizing its interactions with other polymers/fillers are outlined, bearing repercussions on the resultant materials properties. This review emphasizes the structure–process–property relationships of these multiphase systems in bulk and highlights synergistic effects and potential impediments to property improvements. It surveys prospective applications for alginate-based multiphasic bulk materials, spanning membrane separation, controlled release, wound healing, tissue engineering, food packaging, and agricultural domains. Finally in this field, knowledge gaps have been identified and future research directions are suggested.</p

Natural Fibers, Bio- and Nanocomposites

The field of bio- and nano- polymer composite materials for advanced structural and medical applications is a fast emergent area and subject of scientific attention. Natural fibers have received great interest as fillers for polymer composites because of the environmental issues in combination with their low cost. Cellulose nanofibers reinforced polymer composites is a fast growing area of research because of their enhanced mechanical, thermal and biodegradation properties. Composites with polymer matrices and cellulose nanofibers are increasingly regarded as an alternative to conventional composites. The properties of nanocomposite materials depend not only on the properties of their individual constituents but also on their morphology and interfacial characteristics. This rapidly expanding field is generating many exciting new materials with novel properties. The special issue will be interesting for researchers working in this field as it will deals with cellulose fibers, nanofibers and covers the latest advances in bio- and nano- polymer composite materials