Search

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.

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.

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

A series of silyl-amide complexes (=M{N(SiMe3)2}2) were examined as the catalysts for the ring-opening polymerization (ROP) of L-lactide. The catalytic activity of the silyl-amide complexes for zinc was compared with that of the silyl-amide complexes of tin in order to clarify the structural effects on the catalytic behavior. In the tin complexes, the addition of 1-dodecanol made the polymerization rate of L-lactide faster and suppressed the initiation with the N(SiMe3)2 ligands. The 1H NMR analysis revealed that the rates of ligand exchange for the N(SiMe3)2 and 1-dodecanol are different between the zinc and tin complexes. Based on this finding, melt polymerizations of L-lactide was conducted with the zinc catalyst to synthesize high-molecular-weight poly(L-lactide). The M n of the obtained polymer was found to become higher than 60,000 Da, which is required for the industrial application of polylactide, in a short reaction time.

The stereo diblock (d-sb-PLA: PDLA-PLLA) and triblock (t-sb-PLA: PDLA-PLLA-PDLA) were synthesized by terminal Diels-Alder coupling of anthracene-terminated PLLA and maleimide-terminated PDLA. The d-sb-PLA and t-sb-PLA were found to form the stereocomplex crystals of PLLA and PDLA showing excellent thermo-mechanical properties.

The enzymatic polymerization of 12-hydroxystearic acid (12-HSA) was carried out with Lipase CA® in benzene to produce poly(12-hydroxystearate) (PHS) with a low molecular weight. When this polymerization was continued for a long reaction time, the PHS once formed was depolymerized into a cyclic diester, 13,16-dihexyl-1, 14-dioxacyclohexacosane-2,15-dione (12-HSAD). Similar polymerization and depolymerization were observed when 12-hydroxyoleic acid (12-HOA) was treated with Lipase CA®, whereas only polymerization occurred when 12-hydroxydodecanoic acid (12-HDA) was treated in a similar manner. The preferential formation of cyclic diesters for 12-HSA was attributed to the structural requirements due to the bulkyn-hexyl side groups stemming from the ring systems.

Bio-based polymers are made from bio-originated feedstocks. Among those developed thus far, polylactides (PLA) stand at the forefront of practical use and are now manufactured on a commercial scale. However, the application of PLAs has been rather limited because of their higher cost, inferior thermal and mechanical properties, and worse processability as compared to the conventional oil-based polymers. Much effort has therefore been made to address it. Our major approach is to develop a direct polycondensation method to synthesize PLA and to use stereoblock-type PLA (sb-PLA) consisting of enantiomeric poly(L-lactide) (PLLA) and poly(D-lactide) (PDLA) because it can easily form stereocomplex (sc) showing a high melting temperature. Other specialty bio-based polymers are also synthesized for application to high-value fields. Particularly, with amphiphilic copolymers consisting of PLA and poly(oxyethylene) (PEG), new morphology change and sol-gel process have been disclosed. New bio-based polymers consisting of bio-derived monomeric units have also been synthesized to demonstrate their special functions. In addition, molecular and material design has been done with other biobased polymers such as poly(butylene succinate) (PBS) and poly(3-hydroxyalkanoate)s (PHA).

Poly(vinyl alcohol) (PVA) layers of different thicknesses were intercalated into stereocomplex films composed of poly(L-lactide) and poly(D-lactide). The immersion of composite films into boiling water selectively extracted the water-soluble PVA components, resulting in porous stereocomplex films. The hydrolytic properties of the porous films under alkaline conditions were then quantitatively analyzed. It was observed that the hydrolytic rates decreased with increasing pore sizes.

Enantiomeric poly(lactide)s were assembled by casting solutions of poly(L-lactic acid) and poly(D-lactic acid) with different drying process and annealing procedures. Crystallization in these films was studied by differential scanning calorimetric study and wide-angle X-ray diffraction. Stereocomplex crystallization occurred more predominantly than homo crystal during casting and annealing. Atomic force microscopic observation showed solution-grown single crystal like structure on the substrate surface. We found that stereocomplex crystal formation was enhanced via homo crystal formation. On the basis of these findings, a mechanism is proposed for the crystallization of enantiomeric poly(lactic acid)s when they are cast from dilute solution.

Nanoparticles of poly(phenyl/methylsilsesquioxane) (PPMSQ) were prepared by emulsion polymerization of the co-hydrolysate that had been formed from a mixture of trichlorophenylsilane (TCP) and trichloromethylsilane (TCM) in aqueous solution. The average size of the resultant particles was controlled from 30 to 250 nm in diameter by changing the initial concentration of the co-hydrolysate and the amount of the emulsifier added. The PPMSQ formed from the hydrolysate of TCP/TCM had a high cross-linking density, being insoluble and stable in nature. The 1 H NMR spectrum of the co-hydrolysate revealed that both the primary hydrolysates of TCP and TCM are involved in the fast co-polycondensation to afford meta-stable water-soluble oligomers having many silanol groups. These oligomers are allowed to react with each other to form the nanoparticles with the aid of emulsifier.

The damage imposed on SiOx deposited nylon 6 films as a result of abrasion with a cotton cloth and Gelboflex testing was examined by evaluating the rate at which copper plates, which were enveloped by the damaged films, were corroded by H2S. Abrasion with a cotton cloth caused some micro-cracking of the SiOx layer and the permeation rate of H2S approached that of the uncoated nylon 6 film. Damage to the SiOx layer by twisting and crushing progressed gradually with the number of Gelboflex test cycles and correspondingly the corrosion rate of the copper plates increased. Comparison of the corrosion rates of the copper plates kept in the pouches made of various commercial films with those obtained for the damaged SiOx deposited nylon 6 films showed a clear relationship between the H2 permeation rate of the films and the corrosion rate of the copper plates by H2S.

Cell attachment and proliferation on the polymer films of triblock copolymer(ester-ether)s comprising poly(L-lactide)(PLLA) and poly(oxyethylene-co-oxypropylene)(PN) were investigated using 3T3 fibroblasts. It was found that on the tissue culture polystyrene(TCPS) and the PLLA control film the cells could spread well while on the copolymer films the cells showed a rounded morphology without spreading and proliferated weakly. Especially, little cells proliferated on the films of copolymer having a LN composition of 20 wt%. While the water absorption of the copolymer films increased with increasing PN content, the contact angle against water of copolymer films immersed in aqueous medium was almost identical, being slightly lower than that of the PLLA film. These properties were compatible with the results of cell attachment. Thein vitro hydrolysis of the films of triblock and multiblock type copolymers was faster with increasing PN content. The increased hydrolyzability, the flexibility and the decreased cell attachment suggested that these copolymers may have high potential as biodegradable materials for medical use.

Spherical nano-particles of Poly(phenylsilsesquioxane) (PPSQ) were prepared by emulsion polymerization of phenylsilanetriol (PST) that had been formed in aqueous solution after hydrolysis of trichlorophenylsilane (TCP). The average size of the resultant particles was controlled from 30 nm to 110 nm in diameter by changing the amount of the emulsifier added to the solution. The PPSQ forming the particles was low molecular weight oligomer, consisting of silanol groups that can be utilized as functional groups for further chemical modification.

A thermosetting epoxy resin was found to form polymer particles spontaneously in a stationary reaction system using polyethers as solvents. Poly(oxypropylene) and its copolymer with poly(oxyethylene) were effectively used as reaction media. The diameter of the resultant particles depended on the structure of the amines used as hardeners as well as on the molecular weight and composition of the polyether media. The glass-transition temperatures of the particles revealed that a small amount of polyether used as the medium was incorporated in the epoxy resin particles during the polymerization.

A tetracyclo(phenylsilsesquioxane) (T4) was first synthesized by the oligomerization of the low molecular weight hydrolysate of trichlorophenylsilane (TCP) by catalysis of the weak base, NaHCO 3 . followed by KOH-catalyzed polycondensation in toluene to form poly(phenylsilsesquioxane) (PPQS). The rate of polycondensation of T4 was much slower than that of direct polycondensation of the TCP hydrolysate under identical conditions. The molecular weight of the former product (M n =35800) was significantly lower than that of the latter product (M n =110000). X-Ray scatterings of the PPQS prepared by both processes were slightly different, probably due to the difference in structural regularity or branched structure. These data suggest that the polycondensations of T4 and the TCP hydrolysate should be driven through different reaction mechanisms, although the formation of the double strand ladder chain in the produced PPQS should be common to both.

Various hydrolysates of trichlorophenylsilane (TCP) and their polycondensates were reacted with trichlorosilane for capping the silanol groups formed in defect points of the ladder structure. The 1H NMR spectra of the capping products obtained showed several signals due to the Me3Si groups in different environment. Particularly, the polycondensate prepared from the TCP hydrolysate having higher molecular weight showed both sharp and broad Me3Si signals, suggesting a core-shell type branched structure. No Me3Si signal was shown in the polycondensate prepared from the hydrolysate with low molecular weight, supporting an almost perfect ladder structure with few bonding defects. The wide angle X-ray scattering (WAXS) of this polycondensate showed clear Debye-Scherrer rings due to the crystallization of the polymer chains having the regular ladder structure. The structural regularity of this polycondensate was also supported by the 29Si NMR spectrum. This polymer, having a stable double-strand structure, was found to undergo no base-catalyzed depolymerization in solution. A stepwise polycondensation is proposed for the formation of the ladder polymer in which the trivalent (T0: PhSi(O−)3) or divalent (T1: PhSi(OSi)(O−)2) siloxyl units should be involved in the reaction, leaving the monovalent siloxyl (T2: PhSi(OSi)2(O−)) units unreacted.

The present paper describes the cationic ring-opening polymerization of 2-alkoxy-4,5-dihydro-1,3-oxazol-5-ones derived from L-valine, (L-isoleucine, L-leucine with methyl trifluoromethanesulfonate (MeOTf) as the initiator. The polymerization of these oxazolones proceeded successfully below 0°C and gave poly(N-alkoxycarbonyl-α-amino acid)s in moderate yields. The ease of polymerization was dependent on the 2- and 4-substituents of the oxazolone ring and the combination of bulky groups strongly reduces it. The reaction of 2-ethoxy-4,4-dimethyl-4,5-dihydro-1,3-oxazol-5-one with a catalytic amount of MeOTf did not produce a polymer, but yielded a bicyclic dimer, selectively.

Trichlorophenylsilane (TCP) was hydrolyzed in an toluene/water heterogeneous solvent system, and a low molecular weight hydrolysate with simple structure was isolated from the aqueous solution while a high molecular weight hydrolysate with complicated structure was isolated from the toluene layer. When this hydrolysis was conducted strictly at 0°C, the primary hydrolysate consisting mainly of phenylsilanetriol (PST) could be crystallized out from the aqueous layer. When the low molecular weight hydrolysate obtained from the aqueous layer was subjected to the KOH-catalyzed polycondensation in refluxing toluene, poly(phenylsilsesquioxane) (PPQS) with a highly ordered ladder structure could be obtained. Its molecular weight increased with decreasing molecular weight of the initial hydrolysate, and its silanol content oppositely decreased with it. Since this polycondensation proceeded stepwise, it has been considered that intramolecular cyclization is favored in the first condensation of the low molecular weight hydrolysate and that the resultant higher oligomers are then connected into high polymer with ladder structure by the silanol coupling. The molecular weight of PPQS finally obtained reached 120 kDa.

B,B,B-triaminoborazine (TAB), a molecular precursor for boron nitride (BN), was prepared by amine-exchange reaction of B,B,B-tris(diethylamino)borazine with liquid ammonia in a pressure bottle. The1H NMR spectrum of TAB purified by sublimation revealed that TAB forms a dimer in solution with coordination between B and N atoms at four sites. When TAB was directly pyrolyzed up to 1800°C, hexagonal or turbostratic BN was formed. TAB underwent thermal condensation at 100–200°C to form an oligomeric condensate, which was compressed to a circular disk and sintered to a BN ceramics.

The present paper describes the terpolymerization involving 2-phenyl-1,3,2-dioxaphospholane, methyl acrylate, and carbon disulfide, which took place without any added initiator in benzonitrile or dimethylformamide. The structure and composition of terpolymer were determined by NMR and IR spectra, as well as by elemental analysis. A reaction scheme proceeding via zwitterion Open image in new window was proposed (Eq. 2–5).

Lipase from Candida cylindracea was immobilized by entrapment with photo-crosslinkable resin prepolymers or urethane prepolymers, and by covalent binding or by adsorption to different types of porous inorganic or organic supports. All of the immobilized lipase preparations thus obtained showed some activity for hydrolysis of olive oil. Lipase entrapped with a hydrophobic photo-cross-linkable resin prepolymer exhibited the highest activity, which was about 30% of that of the free counterpart. Entrapment method enabled lipase to gain operational stability. Semicontinuous hydrolysis of olive oil using immobilized lipase was also accomplished in a packed-bed reactor with a recycling system. In this reactor, immobilized lipase was observed to have the sufficient activity and stability.

Spontaneous alternating copolymerizations of 2-phenyl-1,3,2-dioxaphospholane (MN) with p- and with o-formylbenzoic acids (ME) were examined. The copolymerizations took place without catalysts affording the copolymer 3 via zwitterion 6. The copolymerizations involve the oxidation of the phosphorus monomer and the reduction of formylbenzoic acid. The scheme of the copolymerizations was presented. The yields of copolymers were quite different between these two copolymerizations. With ortho acid, the copolymer yield was low due to producing phthalide 4.

This paper describes a group of anti-electrostatic agents 1 for polyamide fiber(Nylon 6). Agents 1 are calcium imidazolinium-carboxylates having poly(oxyethylene) chain and long alkyl group (C11H23 and C17H35). Eight derivatives of 1 were prepared by a four-step one-pot synthesis shown in Scheme 1. Nylon 6 fibers and films containing some of 1 (1.0 and 2.0 wt%) show improved anti-electrostatic property. The performance of 1 was increased by the increase of the length of poly(oxyethylene) chain.