Synthesis of poly(ester carbonate) copolymers

The synthesis of poly(ester carbonate) copolymers based on bisphenol A, terephthalic acid, and phosgene is reviewed, and a new synthetic route is described leading to polymers which are different from those obtained by methods described in the literature. The most important features of the new method are quantitative incorporation of the dicarboxylic acid into the polymer and absence of undersirable side reactions. Synthesis of the random copolymer in which the dicarboxylic acid and carbonic acid groups are present in about equal molar amounts is discussed. Solution properties, effects of M?_n and copolymer composition on T_g, sequence length distribution, the effect of ester interchange reactions on molecular weight distribution, and effects of monofunctional chain termination on molecular weight of the final product are also discussed.     

Thermal degradation of poly(siloxane-urethane) copolymers

The aim of this study was to investigate the characteristics and mechanism of the degradation of poly(siloxane-urethane) (PSiU) copolymers by thermogravimetric analysis (TGA) and TGA coupled with Fourier-transform infra-red spectroscopy (TG-FTIR). The PSiU copolymers consisted of 4,4′-diphenylmethane diisocyanate (MDI), 1,4-butanediol (1,4-BD), and OH-terminated polydimethylsiloxane (PDMS). In TGA they exhibited a two-stage degradation at 250-650 °C. The two stages of degradation have been found to comprise eight degradation steps and two interchange reactions, as revealed by TG-FTIR analysis. The main decomposition products have been identified as CO₂, tetrahydrofuran, cyclosiloxane, and macrocyclic species. In addition, the effects of hard segment content (HSC) on the degradation and thermal stability of PSiU copolymers have been investigated by means of TG and DTG curves; notably, a stability region at 410-470 °C is caused by the cyclosiloxane, as verified by TG-FTIR.     

Thermal degradation of poly(diethyleneglycol-bis-allyl carbonate)

The assisted thermal degradation of poly(diethyleneglycol-bis-allyl carbonate), poly-CR 39, has been investigated at 300°C, under nitrogen or argon, in the presence of the metals, Fe, Cu and Zn. The major decomposition products are carbon dioxide, ethene, propene, 1,4-dioxane, 2-propen-1-ol, 2,2′-oxydiethanol carbonate, 2,2′-oxydiethanol and 1,2-di(2′-hydroxy)ethoxy ethane. A degradation mechanism is proposed.     

Thermal and weathering degradation of poly(propylene carbonate)

High molecular-weight poly(propylene carbonate) (PPC) can remain intact upon storage in ambient air or in water for 8 months once the catalyst is completely removed. Catalyst-free pure PPC is also thermally stable below 180 °C. At 200 °C, degradation occurs, mainly due to attack of the chain-ended hydroxyl group onto a carbonate linkage, through which the molecular weight distribution is broadened by simultaneous formation of low and high molecular weight fractions. Incomplete removal of hydrogen peroxide generated during the catalyst preparation results in a prepared polymer that contains a substantial amount of polymer chains grown biaxially from hydrogen peroxide, which gives rise to more severe thermal degradation. Experiments conducted in a weathering chamber at high temperature (63 °C) and high humidity (50%) revealed another degradation process involving chain scission through an attack of water molecules onto the carbonate linkage, which progressively and temporally lowers molecular weight.     

Studies on heat-resistant poly(metal phthalocyanine)-imide copolymers

Several new poly(metal phthalocyanine)imide copolymers have been prepared using 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BPTDA), metal(11) 4,4′,4″,4″′-phthalocyanine tetraamines (MPTA), p-phenylenediamine, 4,4′-methylenedianiline, and 9,9-bis(4-aminophenyl)-fluorene (BAF). The attractive feature of these polymers is their high thermooxidative and thermal stability. The polymer decomposition temperatures of all the imide copolymers are greater than 500°C in air and N atomspheres. Another noteworthy property is their high char yield: 60–78% at 800°C in a N₂ atmosphere. Variation of the metal phthalocyanine concentration has a remarkable effect on the thermal stability and degree of polymerization. The most preferred molar proportion of the reagents MPTA, diamine, and BTDA is 1.25:7.5:10. These polymers may be useful in the preparation of heat-resistant films and fibers.     

Synthesis and hydrolytic degradation of poly(ethylene succinate) and poly(ethylene terephthalate) copolymers

The conditions of synthesis of statistical poly(ethylene succinate-co-terephthalate) copolymers (2GTS) and high molecular weight poly(ethylene succinate) (PES) with good hydrolytic and optical parameters, designed for the production of biodegradable products and resins, are presented in this article. Copolymers were prepared by melt polycondensation of bis-(β-hydroxyethylene terephthalate) (BHET) and succinic acid (SA) with excess of ethylene glycol (2G) in the presence of a novel titanium/silicate catalyst (C-94) and catalytic grade of germanium dioxide (GeO₂) as cocatalyst. The chemical structure and physical properties of those materials were characterized by ¹H NMR, FT-IR, dynamical-mechanical thermal analyses (DMTA), differential scanning calorimetry (DSC), solution viscosity and spectroscopic methods. The hydrolytic degradation was performed in a water solution with variable pH, also in garden soil and in compost. The highest hydrolytic degradation rate was observed for pH 4 and for compost. Better hydrolytic degradation values in compost medium were observed for copolyester prepared in the presence of GeO₂ as polycondensation cocatalyst. The copolyester with 40 mol% of aliphatic units was chosen for industrial syntheses which were performed in ELANA and subsequently the processing parameters and compatibility with potato starch of this polyester were checked by BIOP Biopolymer Technologies AG.     

Synthesis and in vitro degradation of poly(alkylene carbonate anhydride)

A novel degradable poly(alkylene carbonate anhydride) (PACA) was synthesized by the melt polycondensation reaction of the corresponding mixed anhydrides of the dicarboxylic acid derived from oligo(tetramethylene carbonate)diol (OTMCD) and oligo(hexamethylene carbonate)diol (OHMCD). The polymer's structure was confirmed by IR and ¹H NMR spectroscopy. DSC analysis showed PACA had a low T_g (< –30°C). In vitro degradation tests indicated that the degradation rate of poly(alkylene carbonate) was more controlled with the incorporation of anhydride groups.     

Hydrophilic–hydrophobic AB diblock copolymers containing poly(trimethylene carbonate) and poly(ethylene oxide) blocks

AB‐type block copolymers with poly(trimethylene carbonate) [poly(TMC); A] and poly(ethylene oxide) [PEO; B; number‐average molecular weight (M_n) = 5000] blocks [poly(TMC)‐b‐PEO] were synthesized via the ring‐opening polymerization of trimethylene carbonate (TMC) in the presence of monohydroxy PEO with stannous octoate as a catalyst. M_n of the resulting copolymers increased with increasing TMC content in the feed at a constant molar ratio of the monomer to the catalyst (monomer/catalyst = 125). The thermal properties of the AB diblock copolymers were investigated with differential scanning calorimetry. The melting temperature of the PEO blocks was lower than that of the homopolymer, and the crystallinity of the PEO block decreased as the length of the poly(TMC) blocks increased. The glass‐transition temperature of the poly(TMC) blocks was dependent on the diblock copolymer composition upon first heating. The static contact angle decreased sharply with increasing PEO content in the diblock copolymers. Compared with poly(TMC), poly(TMC)‐b‐PEO had a higher Young's modulus and lower elongation at break. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4819–4827, 2005     

Thermal degradation of poly(tetramethyl-p-silphenylene) siloxane homopolymers and copolymers in nitrogen

The thermogravimetry (TGA) in nitrogen was measured for poly(tetramethyl-p-silphenylene)-siloxane (TMPS) fractions with narrow molecular weight distributions and for block copolymers of TMPS and dimethyl siloxane (DMS) with varying composition. The measurements were made with the Perkin-Elmer DCS IB-TGA attachment which consists of a Cahn electrobalance and a wire-wound furnace with programmable temperature controls. The weight loss curves for heating rates of 10, 20, and 40°C/min were analyzed using the method of Flynn and Wall. The analysis indicates that thermal degradation proceeds primarily by scission of the siloxane bond with an activation energy of 44 ± 3 kcal/mole for the uncatalyzed reaction and 13 ± 2 kcal/mole for the reaction occurring in the presence of residual catalyst. The thermal stability of the TMPS–DMS copolymer is impaired through increasing the concentration of the DMS component. Cyclic DMS trimer and TMPS monomer and dimer were observed by mass spectrometry which gave results consistent with the proposed mechanism of degradation.     

Nanosized amorphous calcium carbonate stabilized by poly(ethylene oxide)-b-poly(acrylic acid) block copolymers

Particles of amorphous calcium carbonate (ACC), formed in situ from calcium chloride by the slow release of carbon dioxide by alkaline hydrolysis of dimethyl carbonate in water, are stabilized against coalescence in the presence of very small amounts of double hydrophilic block copolymers (DHBCs) composed of poly(ethylene oxide) (PEO) and poly(acrylic acid) (PAA) blocks. Under optimized conditions, spherical particles of ACC with diameters less than 100 nm and narrow size distribution are obtained at a concentration of only 3 ppm of PEO-b-PAA as additive. Equivalent triblock or star DHBCs are compared to diblock copolymers. The results are interpreted assuming an interaction of the PAA blocks with the surface of the liquid droplets of the concentrated CaCO3 phase, formed by phase separation from the initially homogeneous reaction mixture. The adsorption layer of the block copolymer protects the liquid precursor of ACC from coalescence and/or coagulation.     

Fluorine-containing poly(carbonate-block-siloxane) copolymers

On the basis of carbofunctional oligo(??,??-bisphenoxy-trifluoropropyl(methyl)siloxanes, bisphenols, and bisphenol A bis(chloroformate), novel fluorine-containing poly(carbonate-block-siloxanes) are synthesized and characterized. The presence of trifluoropropyl groups in siloxane blocks of the copolymers decreases the sorption of hydrocarbons by 4 to 6 wt % instead of the 60 wt % for usual poly(carbonate-block-dimethylsiloxanes). Films based on fluorine-containing poly(carbonate-block-siloxanes) retain their high strength characteristics in the swollen state (??_b = 20 MPa).     

Studies of photooxidative degradation of poly(vinyl chloride)/poly(ethylene oxide) blends

The photooxidative degradation of blends (in a full range of compositions) of amorphous poly(vinyl chloride) (PVC) with semicrystalline poly(ethylene oxide) (PEO) in the form of thin films is investigated using absorption spectroscopy (UV–visible and Fourier transform infrared) and atomic force microscopy (AFM). The amount of insoluble gel formed as a result of photocrosslinking is estimated gravimetrically. It is found that the PVC/PEO blendsí susceptibility to photooxidative degradation differs from that pure of the components and depends on the blend composition and morphology. Photoreactions such as degradation and oxidation are accelerated whereas dehydrochlorination is retarded in blends. The photocrosslinking efficiency in PVC/PEO blends is higher than in PVC; moreover, PEO is also involved in this process. AFM images showing the lamellar structure of semicrystalline PEO in the blend lead to the conclusion that the presence of PVC does not disturb the crystallization process of PEO. The changes induced by UV irradiation allow the observation of more of the distinct PEO crystallites. This is probably caused by recrystallization of short, more mobile chains in degraded PEO or by partial removal of the less stable amorphous phase from the film surface. These results confirm previous information on the miscibility of PVC with PEO. The mechanism of the interactions between the components and the blend photodegradation are discussed. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 585–602, 2004     

Thermal decomposition behavior of poly(propylene carbonate) in poly(propylene carbonate)/poly(vinyl alcohol) blend

Journal of Thermal Analysis and Calorimetry - To provide guidance for the practical thermal processing and applications of poly(propylene carbonate)/poly(vinyl alcohol) (PPC/PVA) blend, an...     

聚碳酸丙烯酯中碳酸丙烯酯含量的测定

建立了气相色谱分析聚碳酸丙烯酯中碳酸丙烯酯含量的方法,该方法操作简单,准确度高,可满足工业检测需求.     

Two-dimensional chromatography applied to the study of the thermo-oxidative degradation of poly(styrene-b-butadiene) star block copolymers

Two-dimensional chromatography with gradient polymer elution chromatography in the first dimension and gel permeation chromatography in the second dimension was used to characterize a poly(styrene-b-butadiene) star block copolymer. The data evidence several populations that are clues left by the different steps in the sequential reaction employed to make the polymer. The sample was subjected to thermo-oxidative degradation at 180°C and was analyzed at different times during the process. After a relatively long induction period, the two-dimensional chromatograms show how the different populations are progressively degraded via random chain scission of the polybutadiene block to leave essentially polystyrene as the only soluble component. With longer thermal aging times, the polystyrene also degrades via chain scission.     

Thermal degradation kinetics of thermoresponsive poly(N-isopropylacrylamide-co-N,N-dimethylacrylamide) copolymers prepared via RAFT polymerization

Reversible addition-fragmentation chain transfer polymerization at 70 °C in N,N-dimethylformamide was used to prepare poly(N-isopropylacrylamide-co-N,N-dimethylacrylamide) copolymers in various compositions to afford well-defined polymers with pre-determined molecular weight, narrow molecular weight distribution, and precise chain end structure. The copolymer compositions were determined by ¹H NMR spectroscopy. The reactivity ratios of N-isopropylacrylamide (NIPAM) and N,N-dimethylacrylamide (DMA) were calculated as r _NIPAM = 0.838 and r _DMA = 1.105, respectively, by the extended Kelen–Tüdös method at high conversions. The lower critical solution temperature of PNIPAM can be altered by changing the DMA content in the copolymer chain. Differential scanning calorimetry and thermogravimetric analysis at different heating rates were carried out on these copolymers to understand the nature of thermal degradation and to determine its kinetics. Different kinetic models were applied to estimate various parameters like the activation energy, the order, and the frequency factor. These studies are important to understand the solid state polymer degradation of N-alkyl substituted polymers, which show great potential in the preparation of miscible polymer blends due to their ability to interact through hydrogen bonding.     

Thermal degradation of poly(vinyl bromide), vinyl bromide-methyl methacrylate copolymers,and poly(vinyl bromide)-poly(methyl methacrylate) blends

Degradation behavior has been compared for PVB, five VB-MMA copolymers which span the composition range, PMMA, and PVC by using thermogravimetry in dynamic nitrogen and thermal volatilization analysis (TVA) under vacuum for programmed heating at 10°C/min. Volatile products have been separated by subambient TVA and identified. PVB is substantially less stable than PVC but shows inmost respects analogous degradation behavior. The introduction of VB into the PMMA chain leads to intramolecular lactonization with release of methyl bromide at temperatures a little above 100°C; after this reaction is complete, however, the polymer is more stable toward volatilization than PMMA. Copolymers with moderate and high VB contents also lose hydrogen bromide. Carbon dioxide is a significant product at intermediate compositions. The variation of product distribution with copolymer composition is discussed in relation to the several reactions involved and comparisons are made with VC-MMA copolymers. PVB-PMMA blends snow some features of degradation behavior in common with the PVC-PMMA system but also very important differences. The effect of PVB is only to stabilize the PMMA; the mechanism is discussed. The role of PVB as an additive and VB as a comonomer for fire-retardant PMMA compositions is briefly considered in relation to earlier studies.     

Thermal degradation of poly(vinyl chloride): effect of oxygen on the thermal degradation of poly(vinyl chloride)

On the basis of the simultaneously measured free radical generation and HCl evolution a mechanism accounting for the effect of the oxygen on the degradation of poly(vinyl chloride) (PVC) is proposed. The mechanism is based on the reaction of oxygen with radicals generated in PVC to form unstable peroxy radicals. In addition, it is proposed that oxygen reacts directly with conjugated polyenes to form peroxy linkage.