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The current research unfolds the effect of block lengths, microdomain morphology and stereocomplexation on the mechanical properties of PLA-b-PCL-b-PLA triblock copolymers where PCL is involved to improve the poor extensibility of PLA. The linear triblock copolymers PLLA-b-PCL-b-PLLA and PDLA-b-PCL-b-PDLA (PLLA:poly (L-lactic acid) and PDLA:poly (D-lactic acid)) are made by two step ring opening polymerization and blended in a 1 : 1 ratio to achieve stereocomplex blends where the molecular weight of the terminal and the mid segment is tailored. The mechanical strength and elongation at break range from 13 MPa to 36 MPa and 540 to 950%, respectively, for the triblock copolymers with varied block lengths. Such wide-ranged mechanical properties are ascribed to the morphology of the self-assembled nanostructure of triblock copolymers as corroborated with the small angle X-ray scattering (SAXS) results. To render it industrially viable, the process of triblock copolymer synthesis is scaled up to ∼500 g batch followed by its processing using a twin-screw extruder to make a filament which is used for 3D printing of a mesh-type scaffold. The synthesized materials are tested for their biocompatibility by performing MTT assay using rat bone osteosarcoma (UMR-106) cells which renders them as potential biomaterials.

The current research concentrates on the synthesis of linear block copolymers with their backbone consisting of hard and soft segments, that is, poly(L-lactic acid) (PLLA)/ poly(D-lactic acid) (PDLA) and poly(e-caprolactone) (PCL), with the detailed investigation of the effect of block length on the thermal, mechanical, and crystallization behavior followed by their processing and biocompatibility evaluation. In the current work, sequential ring opening polymerization has been employed wherein PCL is used as a macroinitiator for the synthesis of diblock (PCL-PDLA and PCL-PLLA) and stereotriblock copolymers (PCL-PLLA-PDLA) of targeted molecular weight, which is confirmed by 1H NMR spectroscopy. The block length of PCL, in the case of diblock copolymer, is fixed; however, that of PLLA or PDLA is varied, and the enantiomeric blends thereof are made to achieve the merits of stereocomplexation. The length of the individual blocks is the same in the case of stereotriblock copolymer. The presence of two crystall...

Most petroleum-derived plastics, as exemplified by poly(ethylene terephthalate) (PET), are chemically inactive and highly resistant to microbial attack. The accumulation of plastic waste results in environmental pollution and threatens ecosystems, referred to as the “microplastic issue”. Recently, PET hydrolytic enzymes (PHEs) have been identified and we reported PET degradation by a microbial consortium and its bacterial resident, Ideonella sakaiensis. Bioremediation may thus provide an alternative solution to recycling plastic waste. The mechanism of PET degradation into benign monomers by PET hydrolase and mono(2-hydroxyethyl) terephthalic acid (MHET) hydrolase from I. sakaiensis has been elucidated; nevertheless, biodegradation may require additional development for commercialization owing to the low catalytic activity of these enzymes. Here, we introduce PET degrading microorganisms and the enzymes involved, along with the evolution of PHEs to address the issues that hamper microbial and enzymatic PE...

Novel nano-composite emulsions consisting of colloidal silica particles covered with thin polyacrylate coat (PreEm) were successfully prepared with the aid of a nonionic surfactant having a low cloud point (Tcp = 40 °C). This nonionic surfactant first deposited on the surface of colloidal silica particles above its Tcp to provide the sites for adsorption and the following polymerization of acrylic monomer. Scanning transmission electron microscopy of the colloidal particles obtained after the polymerization indicated the presence of very thin coat layer of polyacrylate (c.a., 1–3 nm nm in thickness) around silica nanoparticles. These PreEm particles were readily incorporated into the ordinary acrylic emulsions (AcEm) to obtain silica/ polyacrylate mixed emulsions (PreEm/ AcEm). It was revealed that the mixed emulsions can give transparent coating films at a silica/polyacrylate ratio below 150/100 in which the colloidal particles were distributed in the polymer matrix without aggregation. This morphology was in sharp contrast with the particle aggregation morphologies shown by the films obtained from the naked colloidal silica-AcEm mixed emulsion and the conventional nanocomposite emulsion consisting of silica particles covered with thick polyacrylate coat. The PreEm/ AcEm films exhibited increased hardness with increasing the silica contents to 150%. These data supported the effectiveness of PreEm in controlling the properties of silica-polyacrylate hybrid films.

A high-molecular-weight polyester of poly(mandelate-co-lactate) (PML) is prepared by ring-opening polymerization of stereo-configuration controlled cyclic diester monomers of methyl-6-phenyl-1,4-dioxane-2,5-dione (MPDD) and lactide. The attained PML shows excellent glassy properties, although the original stereo-configuration of MPDD is not preserved. The intrinsic high glass transition temperature (Tg) of PML is promising, and it is able to be further enhanced by thermal treatment to as high as 90 °C. Interestingly, the enhanced high Tg is attained by only 15 mol% of mandelate content in the polymer chain which is far lower than the ones suggested by theoretical calculation. The enhancement in Tg is also attained by polymer blending of PML and poly(l-lactide) (PLLA). The Tg of the polymer blend also reaches 90 °C which is almost 20 °C higher than the ones suggested by theoretical calculations. These results indicate that the rigid mandelate unit consisting of phenyl groups in PML chain effectively interact with PLLA chains in amorphous domain to restrict their chain mobility. The thermal and glassy properties are sufficient to explore new applications in engineering fields.

Melt/solid polycondensation (MP/SSP) of poly( l -lactic acid) (PLLA) was conducted by using several aromatic sulfonic acids as the catalysts. It was clarified that the increase in molecular weight and the thermal stability of the obtained polymer are correlated with the 5% weight loss temperatures (Td,5%) of the sulfonic acids determined by thermal gravimetric analysis. When 2,5-dimethyl-, 2,4-dimethyl- and 4-methyl-benzenesulfonic acids showing Td,5% around 150 °C were used as the catalysts, PLLA polymers with high molecular weight and excellent thermal stability could be obtained. On the other hand, 2,4,6-trimethylbenzenesulfonic acid showing Td,5% around 100 °C and 4-dodecylbenzenesulfonic acid with Td,5% above 200 °C gave PLLA polymers with remarkably low thermal stability. The residual catalyst involved in the product polymer or SO3 generated during the polymerization decreased the thermal stability of the polymer. The oligomeric fractions of the PLLA products were extracted with acetone and analyzed by 1H NMR and mass spectra. It was verified that the catalyst had efficiently been removed by thermal annealing while it remained active during the SSP to produce a thermally stable PLLA with high molecular weight.

Relationship between the increase in molecular weight and evolution of crystal structure was studied in the solid-state polycondensation (SSP) of poly( l -lactic acid) (PLLA). Here, a PLLA prepolymer having a weight-average molecular weight (Mw) of c.a., 3000 Da and a high optical purity (OP) over 99 %ee was prepared by bulk melt-polycondensation of l -lactic acid with dodecylbenzenesulfonic acid as a catalyst. It was first annealed at 80–110 °C and subjected to SSP at 120–140 °C to obtain a PLLA polymer having an Mw higher than 100,000 Da. The highest increase in Mw was observed at 140 °C, while the growth of crystal structure had been induced in an early stage of SSP at 120 °C, reaching 71% in crystallinity. Wide- and small-angle X-ray scatterings of the PLLA polymers revealed that the PLLA polymer retained the α-form crystals throughout the annealing and SSP with little change in lamellar morphology. It was therefore suggested that the acid-catalyzed polycondensation is driven by the reaction of the terminal groups of the PLLA prepolymer accumulated on the surface ab planes of the lamellar crystals above 120 °C. Therefore, the crystal morphology of the annealed samples was found to strongly influence the final molecular weight of PLLA in the SSP.

Multi-sb-PLAs with molecular weights of approximately 60,000 (MSB-60) and 130,000 (MSB-130) with various block lengths were synthesized. These have a structure in which di-block copolymers consisting of L - and D -blocks with the same length are connected with 1,12-dodecanediol (DMG), an initiator and hexamethylene diisocyanate (HMDI), a chain extender alternately. DSC analyses revealed that T g increases with the increase in the block length and the multi-sb-PLA with a lower molecular weight has higher T g at a constant block length. These are attributable to the higher concentration of DMG and HMDI in the multi-sb-PLA. T m increases with the increase in the block length and the molecular weight of multi-sb-PLA and those of MSB-60 and MSB-130 get close to a constant value at higher block length. The variation of T m seems to be attributable to change in the lateral dimension of lamella rather than that of the thickness. T c in the heating process from the amorphous solid decreases and that in the cooling process from the melt increases with the increase in the block length, indicating that the multi-sb-PLA with a long block has a wider temperature range of the crystallization.

Multi-stereoblock PLAs (multi-sb-PLA)s having the controlled block sequences between PLLA and PDLA were synthesized by the chain-extension of tri-stereoblock PLAs. These multi-sb-PLAs only crystallize into the stereocomplex without forming any traces of homo-chiral crystal. The effects of the block length and the total molecular weight on the isothermal crystallization behavior and the higher order structure of the multi-sb-PLAs were investigated. Observation of isothermal crystallization behavior revealed that the multi-sb-PLA with longer blocks and higher molecular weights started the crystallization at a lower temperature within a shorter period of time in a wider temperature range. The crystallization rate increases with increasing block length and the multi-sb-PLA with a longer blocks achieves higher degree of crystal. The multi-sb-PLA with a higher molecular weight forms more complete structure of the spherulite than that with a low molecular weight. Annealing of the amorphous multi-sb-PLA produced sc with two different lamellar thicknesses. One which melts at a higher temperature is a main sc phase with a lamellar thickness merely determined by the block length and the molecular weight regardless of the thermal history. The chains in the amorphous region only crystallized upon annealing and gradually grew with increasing annealing temperature giving some addition to the lamellar thickness of the samples detected by SAXS.

A novel multi-block copolyester, poly(butylene succinate)-multi-poly(butylene terephthalate) (m-PBST), was synthesized by the melt/solid interfacial co-polycondensation of a melt-blend of poly(butylene succinate) (PBS) and poly(butylene terephthalate) (PBT) that had been pre-formed. In this co-polycondensation, the reaction temperature was kept between the melting temperatures (T m) of PBS and PBT so as for the low-melting PBS (melt) to be effectively connected with the high-melting PBT (solid). The succinate content and persistence ratio (r) of the resulting m-PBST were affected by the time of melt-blending of PBS and PBT where their chain-scrambling reaction was induced. The average block number per polymer chain became the largest (7.3) when the blending time was properly adjusted with a PBS to PBT ratio of 2:1. Owing to the block copolymer structure, m-PBST showed thermoplastic properties that should be intermediate between those of PBT and PBS and completely different from those of the corresponding PBS/PBT random copolymer. The enzymatic degradability of m-PBST was also confirmed by the use of Lipase PS® originated from Pseudomonas cepacia. Consequently, m-PBST ought to have potential applications as a new structural material with excellent soft/hard balance and toughness.

In hydrogel-based soft tissue engineering, vascular induction into a hydrogel as well as long-term volume retention is essential to maintain tissue shape and function without causing necrosis in the deeper part of the hydrogel. A silk fibroin (SF) hydrogel shows a sufficiently high mechanical strength to maintain its shape during implantation for a month, but it has not been well evaluated whether it has vascular-inducing bioactivity to achieve its replacement by vascularized tissues. Here, we produced a vascular-inducing peptide (VIP) containing an endothelial cell (EC)-adhesive REDV and vascular endothelial growth factor-mimicking QK peptides to modify the SF hydrogel. In vitro experiments showed that the modification of the SF hydrogel with VIP changed only biological properties of the hydrogel due to the bioactivity of VIP. Subcutaneous implantation of SF hydrogels in rats revealed isotropic EC migration into the hydrogels, which was followed by infiltration of macrophages and fibroblasts. Since these macrophages and fibroblasts appeared to degrade the SF network and to produce collagen, respectively, SF hydrogels were replaced gradually by regenerated tissues. VIP accelerated cell infiltration and doubled the formation of blood vessels in the regenerated tissue. These results suggest the potential of the VIP-modified SF hydrogel as a material for soft tissue engineering applications.

The discovery of Ideonella sakaiensis, a plastic‐degrading bacterium, creates possibilities for a sustainable “bioeconomy” for recycling plastic waste.[Image: see text]

Transparent films were prepared from nano-composite emulsions, which contained nano-size core–shell-type particles (ca. 60 nm in diameter) consisting of colloidal silica (inorganic core, ca. 30 nm in diameter) and poly(methyl methacrylate- co - n -butyl acrylate) (organic shell). The silica content in the film could be increased up to 150 wt/wt% by keeping its homogeneity. It was revealed that the formation of such a core–shell structure is guided by the surface sedimentation of a nonionic surfactant above its clouding point to form an organic thin layer that can provide the sites for monomer absorption and polymerization. The thermal and mechanical properties of the resultant nano-composite films were evaluated by various methods and compared with those of simple blend films of the corresponding acrylic emulsion and colloidal silica. It was clarified that the high-temperature resistance of the nano-composite films can be improved by the reinforcement effect of silica particles.

Stereo multi-block polylactides (multi-sb-PLA) having controlled block sequences of poly(L-lactide) (PLLA) and poly(D-lactide) (PDLA) were synthesized by chain-extension of stereo tri-block polylacitdes (PLLA-PDLA-PLLA) that were readily synthesized by two-step ring-opening polymerization (ROP) of D- and L-lactides. The weight-average molecular weight of the resultant multi-sb-PLAs reached about 14.3 × 104 Da. These multi-sb-PLAs were found to exclusively form stereocomplex (sc) crystals without homo-chiral (hc) crystallization occurring because the quickly formed sc crystals effectively suppressed the hc crystallization as cross-linkers. Their thermal properties could be tuned by controlling the block lengths of PLLA-PDLA-PLLA in the two-step ROP. Particularly, the multi-sb-PLAs consisting of longer PLLA and PDLA blocks in 1:1 ratio exhibited higher sc crystallinity and thermo-mechanical properties after thermal annealing.

In this article, we report the synthesis of a hyperbranched supramolecular polymer composed of continuum of amylose-poly( l -lactide) (PLLA) inclusion complexes by phosphorylase-catalyzed enzymatic polymerization using a branched maltoheptaose-PLLA conjugate according vine-twining polymerization manner. The X-ray diffraction and 1H NMR measurements indicated the presence of the inclusion complex structure in the product. The GPC peak of the amylose segment, which was obtained by alkaline hydrolysis of the vine-twining polymerization product, shifted to the lower molecular weight region, compared with that of the product, supporting the structure of the supramolecular polymer. A hydrogel of the supramolecular polymer was obtained through the formation of an ion gel with an ionic liquid. Furthermore, a cryogel with porous morphology was produced by lyophilization of the hydrogel.

Researchers have attempted to develop efficient antithrombogenic surfaces, and yet small-caliber artificial vascular grafts are still unavailable. Here, we demonstrate the excellent patency of tissue-engineered small-caliber long-bypass grafts measuring 20-30 cm in length and having a 2-mm inner diameter. The inner surface of an acellular ostrich carotid artery was modified with a novel heterobifunctional peptide composed of a collagen-binding region and the integrin α4β1 ligand, REDV. Six grafts were transplanted in the femoral-femoral artery crossover bypass method. Animals were observed for 20 days and received no anticoagulant medication. No thrombogenesis was observed on the luminal surface and five cases were patent. In contrast, all unmodified grafts became occluded, and severe thrombosis was observed. The vascular grafts reported here are the first successful demonstrations of short-term patency at clinically applicable sizes.

Triethoxysilyl-terminated poly(d-lactide)s (eSi-PDLA) were successfully prepared by hydrosilylation of allyl-terminated PDLAs (A-PDLA-ac) which were readily prepared by ring-opening polymerization of d-lactide and the following terminal protection by acetylation. Their acid-catalyzed hydrolysis produced hyper-conjugated PDLAs with terminal silanol coupling. Blend PLLA films containing eSi-PDLA (Mn = 2.1 kDa) in 5-25 wt.% were successfully prepared by the solution casting method. The blend films were found to take a nano-porous or micro-phase separation structure, being different from that of the blend PLLA films containing trimethoxysilyl-terminated poly(d-lactide) (mSi-PDLA) which exhibited particle distribution structure. This difference was reasonably attributed to the different rate of hydrolytic polycondensation of the trimethoxy- and triethoxy-silyl terminals. These results revealed that the competing sterecomplexation/ hyper-conjugation/phase separation can afford specific morphologies, allowing fine control of properties.

Triblock copolymers consisting of poly(oxyethylene) (PEG), poly( d -lactide) (PDLA), and poly( l -lactide) (PLLA) were successfully prepared by the two-step ring-opening polymerization of d - and l -lactides via PEG-PDLA diblock copolymers. These triblock copolymers as well as the diblock copolymer PEG-PDLA and a mixture of enantiomeric diblock copolymers PEG-PDLA/PEG-PLLA were emulsified to make their aqueous micelle solutions. It was found out that the triblock copolymers and the diblock copolymer mixture can form sc crystals in the core to highly stabilize the core–shell particles. In particular, the micelle of a triblock copolymer having a short middle PDLA block gave the smallest particles covered with thin layer of PEG coronas, because the sc crystals had formed around the core–shell interface. These results suggested that the micelle particle morphology can be tuned by changing the core structure even at constant hydrophilic/hydrophobic balance of the block chains.

Mixtures of furan (F)-terminated AB diblock copolymer of F-PEG-PLA and ABA triblock copolymer of PLA-PEG-PLA (PEG: poly(oxyethylene), PLA: poly( l -lactide) (PLLA) or poly( d -lactide) (PDLA) depending on the enantiomeric block chain) having different compositions were readily synthesized by ROP of l - and d -lactides using partially furanylated PEGs as the macro initiators. Mixed micelle solutions of the enantiomeric copolymer mixtures (F-PEG-PDLA/PDLA-PEG-PDLA + F-PEG-PLLA/PLLA-PEG-PLLA) were prepared in the presence and absence of a coupling agent 1,8-bis(maleimido)diethylene glycol (BMG). Both the BMG-free and BMG-added mixed micelle solutions underwent sol–gel transition, and in which the gel strength was found to become much higher in the BMG-added micelle solutions, reaching a level of 11 kPa. These hydrogel systems were thought to be controlled by the dual cross-linking mechanisms for the gel formation: stereocomplex formation between the enantiomeric PLA blocks and Diels–Alder coupling of the furanyl terminals on PEG blocks with BMG. These sol–gel systems producing strengthened gels are versatile for use as injectable scaffolds in the tissue engineering.

Silyl-terminated oligomers of poly(l-lactide) (mSi-PLLA) and poly(d-lactide) (mSi-PDLA) were synthesized by hydrosilylation of allyl-terminated derivatives. They were readily hydrolyzed into hyper-branched polymers having particulate morphology. When a mSi-PDLA oligomer was blended with a PLLA sample (52.5 kDa) in 1–10 wt.-% by solution casting, small cross-linked particles with stereocomplex form were generated and distributed homogenously in the PLLA matrix, and by which the homo-chiral crystallization of PLLA was efficiently suppressed. When another mSi-PLLA oligomer was blended with PLLA, the cross-linked particles formed from mSi-PLLA were amorphous and distributed inhomogeneously. It was, therefore, indicated that the hydrolytic polycondensation of mSi-PDLA and mSi-PLLA was induced during the film casting, changing the inner structure and properties of the blend films with PLLA.

A high-molecular-weight ABA tri-block copolymer ([RS]-PHB/PEG), consisting of poly(3-[RS]-hydroxybutyrate) ([RS]-PHB: A) and poly(oxyethylene) (polyethylene glycol; PEG: B), was synthesized by ring-opening polymerization of [RS]-β-butyrolactone ([RS]-βBL) in the presence of PEG and 1,3-dichlorotetrabutyldistannoxane (DTD) as the catalyst. By using a series of PHB derivatives including the new block copolymer, cell adhesion was evaluated with 3T3 fibroblast cells. It was found out that the attached cells didn't extend on [RS]-PHB, but extended on [R]-PHB although the numbers of the attached cells were very small on both [RS]-PHB and [R]-PHB. [RS]-PHB/PEG exhibited even poorer cell adhesion than [RS]-PHB because of the increased hydrophilic nature due to the PEG segments. Although the amount of fibronectin adsorbed on the surface of [RS]-PHB was higher than that on the surface of [R]-PHB, the cell adhesion became poorer on the fibronectin-pre-adsorbed [RS]-PHB. These differences in cell adhesion among these PHB derivatives were reasonably attributed to their surface properties related with the accumulation of methyl groups.

Some gel types have been reported to prevent left ventricular (LV) remodeling in myocardial infarction (MI) animal models. In this study, we tested biodegradable thermoresponsive gels. Poly(L-lactic acid)–poly(ethylene glycol) (PLLA–PEG) and poly(D-lactic acid)–poly(ethylene glycol) (PDLA–PEG) were synthesized by the polycondensation of l- and D-lactic acids in the presence of PEG and succinic acid. Each of these block copolymers was used to prepare particles dispersed in an aqueous medium and mixed together to obtain a PLLA–PEG/PDLA–PEG suspension, which was found to show a sol-to-gel transition around the body temperature by the stereocomplex formation of enantiomeric PLLA and PDLA sequences. In the present study, the G′ of the PLLA–PEG/PDLA–PEG suspension in the rheological measurement remained as low as 1 Pa at 20 °C and increased 2 kPa at 37 °C. The sol–gel systems of PLLA–PEG/PDLA–PEG might be applicable to gel therapy. The effect of the PLLA–PEG/PDLA–PEG gel injection was compared with that of a calcium-crosslinked alginate gel and saline in a rat MI model. The percent fractional shortening improved in the PLLA–PEG/PDLA–PEG (20.8 ± 4.1%) and alginate gel (21.1 ± 4.8%) compared with the saline (14.2 ± 2.8%) with regard to the echocardiograph 4 weeks after the injection (p

Of the biobased polymers developed to date, poly(l-lactide) (PLLA) is the most widely used in many application fields because of its excellent cost–property balance. However, PLLA is slightly inferior to conventional petroleum-based polymers in terms of thermal resistance and functionality. Various modified polylactides (PLAs consisting of enantiomeric d- and l-lactide units in different sequences and ratios) have recently been proposed and should expand the market for these polymers. The new developments involve polymers of high melting temperature (high-T m polymers) based on stereocomplex-type PLAs (sc-PLA) and stereoblock-type PLAs (sb-PLA) as well as those of high glass transition temperature (high-T g polymers) obtained by unit modification and polymer blending. Various specialty derivatives having excellent flexibility and functionality have also been developed by controlled crystallization, polymer blending, organic–inorganic hybridization, and copolymerization. The molecular weight, terminal groups, copolymer composition, and functionalities must be precisely controlled to enable control of the properties of these PLA polymers. Ordinary PLLA, being biodegradable, is widely used in commodity and agricultural fields as well as biomedical fields, mainly in the form of a film or as a non-woven fabric. The new specialty and high-performance PLA polymers can be used as functional and durable materials. Especially interesting is the applicability of PLLA polymers to 3D printing, particularly in fused deposition manufacturing (FDM).

ABA triblock copolymers of polylactides (PLA: A) and aliphatic polycarbonates (APC: B) were prepared by ring-opening polymerization of d- and l-lactides with poly(hexamethylene carbonate) diol and poly(hexamethylene/pentamethylene carbonate) diol (PHPC) as macro-initiators. The enantiomeric copolymers with similar block sequences (PLLA-APC-PLLA and PDLA-APC-PDLA) were mixed in a 1:1 weight ratio to form a stereocomplex of PLA blocks. The resultant stereo mixtures were found to be more thermally stable (up to 200 °C) than the single block copolymers. Polymer films of the stereo mixtures PLLA-PHPC-PLLA/PDLA-PHPC-PDLA exhibited higher elongation and lower modulus. It was therefore evident that the present enantiomeric block copolymer system can be applicable as a novel thermoplastic elastomer that is environmentally friendly in terms of its biobased nature and the use of carbon dioxide as feedstock. © 2014 Society of Chemical Industry

Both AB diblock and ABA triblock copolymers consisting of poly(L-lactide) (PLLA: A) and poly(ethylene glycol) (PEG: B) were deposited on a silicon surface on which poly(D-lactide) (PDLA) had been preimmobilized. The deposit of the diblock copolymer (PLLA-PEG) formed band structures similar to those observed when the same copolymer was directly deposited on the silicon surface. In contrast, the deposit of the triblock copolymer (PLLA-PEG-PLLA) formed many particulates scattering over the surface. When the PLLA-PEG deposit was subjected to water-soaking, the original band morphology was completely replaced by the particulate morphology that was identical to that of the PLLA-PEG-PLLA deposit. Their FT-IR analyses revealed that both copolymers had been bound through the stereocomplex (sc) formation between the preimmobilized PDLA chains and the PLLA blocks of the copolymers. Grazing-incidence small-angle X-ray scattering (GISAXS) also supported these surface morphologies. It was therefore evident that hydrophilic PEG chains can be immobilized on the PDLA-preimmobilized surface by the sc formation.

Glycopolymers having pendant triazole-linked sialyloligosaccharides were successfully synthesized from free saccharides without any protection of the hydroxy and carboxy groups on the saccharides. The glycomonomers were synthesized by the direct azidation of free saccharides using 2-chloro-1,3-dimethylimidazolinium chloride as a condensing agent followed by copper(I)-catalyzed azide-alkyne cycloaddition. The resultant glycomonomers were copolymerized with acrylamide by a reversible addition-fragmentation chain transfer technique. Each of the glycopolymers were obtained and then immobilized on a gold-coated sensor of quartz crystal microbalance to analyze their binding behavior with the lectin. The glycopolymers strongly bound with the corresponding lectin without nonspecific adsorption in aqueous solution. In addition, the glycopolymer bearing a complex-type sialyl N-linked oligosaccharide was found to strongly bind with both human and avian influenza A viruses. The strong binding, observed using the hemagglutination inhibition assay, was attributed to the glycocluster effect of the glycopolymer and the biantennary structure of the N-linked oligosaccharide.

An oligomer of poly(hexamethylene carbonate) (PHMC) that is synthesized by ester-exchanging polycondensation of ethylene carbonate and 1,6-hexanediol is chain-extended by using diphenyl carbonate as chain extender. The resultant PHMC, dihydroxyl-terminated, is then subjected to tin-catalyzed ring-opening polymerization of L-lactide to prepare ABA tri-block copolymers consisting of poly-L-lactide (PLLA: A) and PHMC (B), which retain significantly high molecular weights even at increased contents of PHMC. Polymer films of these block copolymers exhibit high elongation, reaching 700% at a high PHMC content. It is therefore suggested that the present block copolymer system can be a novel thermoplastic elastomer, which is partly bio-based.

4,6-Dimethoxy-1,3,5-triazin-2-yl glycosides, glycosyl donors prepared in one step from free saccharides without protection of the hydroxy groups, were stereoselectively and equivalently converted t...

Histocompatibility of biodegradable aliphatic polyesters was examined by cell adhesion and cell proliferation tests by using fibroblast 3T3-L1 cells. It was found out that the cell adhesion decreased in the order of polystyrene (PS)>poly(L-lactide) (PLLA)>poly(3-[R]-hydroxybutyrate/valerate) ([R]-PHB/HV)>poly(butylene succinateco-lactide) (PBSL)>poly(3-[RS]-hydroxybutyrate) ([RS]-PHB). Particularly poor cell adhesion was shown for [RS]-PHB even after fibronectin had been pre-adsorbed, and cell proliferation and extension were not observed on [RS]-PHB. These different behaviors in cell adhesion could not be well explained by the differences in wettability and roughness of the film surfaces of these polymers. ATR-FTIR analysis of these films revealed that the surface concentration of methyl groups is significantly higher in the [RS]-PHB film than the other films. It was therefore considered that the poor cell adhesion of [RS]-PHB is attributable to the structural change of the protein adsorbed on the methyl-accumulated surface. Open image in new window

BCB triblock copolymers consisting of poly-L-lactide (PLLA: B) and poly(3-methy-1,5-pentylene succinate) (SA/MPD: C) were first synthesized by ring-opening polymerization (ROP) of L-lactide by using a dihydroxyl-terminated SA/MPD (Mn≈20k) and tin octoate as the macroinitiator and catalyst, respectively. The telechelic dihydroxyl-terminated SA/MPD was readily synthesized by the controlled melt-polycondensation of succinic acid and 3-methyl-1,5-pentandiol (MPD). The resultant triblock copolymers, dihydroxyl-terminated, were subsequently utilized as the macroinitiators in the second-step ROP of D-lactide to obtain ABCBA penta-block copolymers (penta-sb-PLA) consisting of poly-D-lactide (PDLA), PLLA, and SA/MPD as the A, B, and C blocks, respectively. The weight-average molecular weights of the resultant penta-sb-PLAs became higher than 150 kDa. The cast films of these penta-sb-PLAs exhibited flexible nature due to the presence of the SA/MPD soft block as well as excellent heat-stability owing to the easy stereocomplex formation of the neighboring enantiomeric PLLA and PDLA blocks.