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End-functionalized hydroxyethyl methacrylate macromonomers of poly(l-lactide) (HEMA-PLA) were synthesized by the ring-opening polymerization of l-lactide (LA), using mono- and trihydroxyethyl methacrylate-aluminium alkoxides as initiators. The polymerization carried out in toluene at high vacuum and 60°C presented a living character, giving rise to the formation of a linear polymer without cyclization...
Two series of novel polymers were synthesized by reacting l-lactide (LLA) with aminohydroxymethylpropanediol (AHPD) or aminopropanediol (APD) using stannous octoate as catalyst. Nuclear magnetic resonance, Fourier-transform infra-red spectroscopy, gel permeation chromatography (g.p.c.), differential scanning calorimetry (d.s.c.) and thermogravimetric analysis were employed for the characterization...
The effects of annealing on the thermal properties, morphologies and mechanical properties of poly(l-lactide) (PLLA) films were investigated by differential scanning calorimetry, polarizing microscopy and tensile testing. PLLA films prepared by solution casting were annealed by three different processes: process A, direct annealing of the as-cast film; process B, melting and annealing; and process...
Reaction of l-lactide (LLA) with sorbitol (SB) in the presence of stannous octoate (Sn oct), tetraphenyl tin (TPhT) and several other catalysts gave a series of novel polyesters. Several techniques such as nuclear magnetic resonance (n.m.r.) and Fourier transform infra-red (FTi.r.) spectroscopy, gel permeation chromatography (g.p.c.) and differential scanning calorimetry (d.s.c.) were used in order...
Several methods of introducing crosslinks into poly(l-lactide) (PLLA) were studied. Electron beam irradiation was not effective in crosslinking PLLA, and, moreover, caused severe polymer degradation and embrittlement of the material. Peroxide crosslinking of PLLA with dicumyl peroxide (DCP), however, resulted in gelation. At high peroxide concentrations (13–25 wt%) and high curing temperatures (192°C),...
The miscibility of high molecular weight poly(l-lactide) (PLLA) with high molecular weight poly(ethylene oxide) (PEO) was studied by differential scanning calorimetry. All blends containing up to 50 weight% PEO showed single glass transition temperatures. The PLLA and PEO melting temperatures were found to decrease on blending, the equilibrium melting points of PLLA in these blends decreased with...
Solution-grown crystals (SGC) of poly(l-lactide) (PLLA) were prepared from 0.01% (w/w) or 0.08% (w/w) acetonitrile solution by an isothermal crystallization method. Their morphology and structural features were examined by transmission electron microscope with the diffraction mode, wide-angle X-ray diffractometry and atomic force microscope. The molecular chains are packed in the manner perpendicular...
Biodegradable star-block copolymers containing a hydrophilic 4- or 8-arm branched poly(ethylene oxide) (PEO) central unit and hydrophobic poly(l-lactide) (PLLA) or poly(l-lactide-co-glycolide) (PLLG) were synthesized by solution polymerization in toluene catalysed by aluminium triethylene. Using g.p.c. and laser light scattering analysis, a significant increase in the molecular weights could be demonstrated,...
The miscibility of poly(l-lactide) (PLLA)/poly(p-vinylphenol) (PVPh) blends has been studied by differential scanning calorimetry (d.s.c.) and Fourier transform infrared (FTi.r.) spectroscopy. PLLA/PVPh blends are partially miscible as characterized by shifts in the glass transition temperatures (T g s) of the two component polymers. The T g of the PLLA-rich phase increases with...
The crystallization characteristics of poly(l-lactide) (PLLA) films of different molecular weights have been studied by differential scanning calorimetry, optical microscopy and a depolarized-light intensity (d.l.i.) method. In non-isothermal crystallization modes from the isotrophic melt, the crystallinity of PLLA films increased remarkably with a decrease in the cooling rate, accompanied by a kind...
In this work, the immersion precipitation process was used to obtain porous poly(l-lactide) films which were tested as supports for culture of VERO cells. The mechanism of phase separation taking place during the film formation was investigated using light scattering measurements. A theoretical ternary phase diagram was proposed and correlated with the light scattering results. The film morphology...
The side reactions in the synthesis of oxyethylmethacrylate-functionalised poly(l-lactide) macromonomers using aluminium mono- and trialkoxides carrying this functionality have been studied. In addition to the expected changes in the final molecular weight for this kind of polymerisations, changes in the structure of the chain end-groups have been identified by spectroscopic techniques. Radical polymerisation...
We report on anomalous structural organization from core–shell nanoparticles of a hydrophobic/hydrophilic diblock copolymer consisting of semi-crystalline poly(l-lactide) (PLLA) and poly(oxyethylene) (PEG). The copolymer was synthesized and suspended in an aqueous medium to prepare its core–shell particles. The resultant nanoparticles were spread on a germanium substrate to trace the particle aggregation...
Poly(l-lactide) (PLLA) films having different initial crystallinities (x c ) (0–57%) and a fixed crystalline thickness were prepared by annealing the melt at a fixed temperature for different times. Their enzymatic hydrolysis was investigated in the presence of Proteinase K ® . The rate of weight loss decreased rapidly and slowly with an increase in the initial x c for x ...
High molecular weight di- and triblock copolymers of poly(l-lactide), PLLA, (80wt%) with a crystallizable flexible second component such as poly( -caprolactone), PCL, or poly(oxyethylene), PEO, (20wt%) were obtained in nearly quantitative yields by ring opening of l-lactide initiated by PCL or PEO hydroxy terminated macromers. The copolymers were characterized by 1 H NMR and FTIR spectroscopy...
A novel experimental set up consisting of dielectric spectroscopy and small angle light scattering (or potentially any other optical technique used in combination) is introduced. The sample is enclosed in a Dielectric-Optical-Shear (DOS) cell capable of precisely controlling temperature and thickness. This method allows for simultaneous in situ, real-time monitoring of the changes in the molecular...
Among the various inorganic nucleators examined, Talc and an aluminum complex of a phosphoric ester combined with hydrotalcite (NA) were found to be effective for the melt-crystallization of poly(l-lactide) (PLLA) and PLLA/poly(d-lactide) (PDLA) stereo mixture, respectively. NA (1.0phr (per one hundred resin)) can exclusively nucleate the stereocomplex crystals, while Talc cannot suppress the homo...
To achieve the feed stock recycling of poly(l-lactide) (PLLA) to l,l-lactide, PLLA composites including alkali earth metal oxides, such as calcium oxide (CaO) and magnesium oxide (MgO), were prepared and the effect of such metal oxides on the thermal degradation was investigated from the viewpoint of selective l,l-lactide formation. Metal oxides both lowered the degradation temperature range of PLLA...
Crystallization behavior, structural development and morphology evolution in a series of diblock copolymers of poly(l-lactide)-block-poly(ethylene glycol) (PLLA-b-PEG) were investigated via differential scanning calorimetry, wide-angle X-ray diffraction, polarized optical microscopy and atomic force microscopy. In these copolymers, both blocks are crystallizable and biocompatible. It was interesting...
This paper describes a new reactive blending approach to improve the compatibility of poly(l-lactide) (PLLA) and poly(ɛ-caprolacton) (PCL). For this purpose, the ring-opening polymerization of l-lactide (LLA) was carried out in the presence of PCL-OH (OH groups on one end). The P(CL-b-LLA) block copolymers were in situ formed during polymerization, and as a result, PLLA/P(CL-b-LLA) blends were obtained...
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