Synthesis and characterization of alternating copolymer from carbon dioxide and propylene oxide

High yield and pure zinc glutarate catalysts used for copolymerization of carbon dioxide and propylene oxide have been synthesized in different solvents by ultrasonic methodology. For the purposes of comparison, low‐yield zinc glutarates were also synthesized via mechanical stirring method with other synthetic conditions remaining unchanged. Fourier Transform Infrared Spectroscopy and wide‐angle X‐ray diffraction techniques confirmed the presence of high‐quality zinc glutarate catalysts. Accordingly, poly(propylene carbonate) (PPC) can be synthesized from carbon dioxide and propylene oxide using the zinc glutarate catalysts. It was confirmed that the as‐prepared PPC had an alternating copolymer structure together with high molecular weight. The thermal and mechanical properties of the obtained PPC copolymer were determined by means of differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and tensile test. DSC and TGA results showed that the PPC copolymer exhibited high glass transition temperature (39.39°C) and decomposition temperature (278°C) when compared to their corresponding values reported in the literature. Tensile test showed that the PPC film exhibited superior mechanical strength. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2327–2334, 2002     

Catalytic synthesis and characterization of an alternating copolymer from carbon dioxide and propylene oxide using zinc pimelate

New zinc pimelate catalysts used for copolymerization of carbon dioxide and propylene oxide have been synthesized in high yield by a magnetic stirring method. The regular molecular structure of the zinc pimelate was confirmed by Fourier‐transform infrared spectroscopy and wide‐angle X‐ray diffraction techniques. Accordingly, poly(propylene carbonate) (PPC) can be synthesized from carbon dioxide and propylene oxide using these zinc pimelate catalysts. High catalytic efficiency (95.2 gram polymer per gram catalyst or 21 300 g of polymer per mole of zinc) was achieved by optimizing the PO/catalyst ratio. NMR measurement revealed that the PPC synthesized had an alternating copolymer structure. The thermal properties of PPC were determined by modulated differential scanning calorimetry and thermogravimetric analysis. The results demonstrated that the PPC copolymer exhibited an extremely high glass transition temperature of 44.27 °C and decomposition temperature of 257 °C, comparable with values reported in literature. Copyright © 2003 Society of Chemical Industry     

Effect of the structure on the morphology and spherulitic growth kinetics of polyolefin in‐reactor alloys

Four polyolefin in‐reactor alloys with different compositions and structures were prepared by sequential polymerization. All the alloys were fractionated into five fractions: a random copolymer of ethylene and propylene (25°C fraction), an ethylene–propylene segmented copolymer (90°C fraction), an ethylene homopolymer (110°C fraction), an ethylene–propylene block copolymer (120°C fraction), and a propylene homopolymer plus a minor ethylene homopolymer of high molecular weight (>120°C fraction). The effect of the structure on the morphology and spherulitic growth kinetics of the polypropylene (PP) component in the alloys was investigated. The polyolefin alloys containing a suitable block copolymer fraction and a larger amount of PP had a more homogeneous morphology, and the crystalline particles were smaller. Quenching the polyolefin alloys led to smaller crystallites and a more homogeneous morphology as well. Isothermal crystallization was carried out above the melting temperature of polyethylene, and the growth of PP spherulites was monitored with polarized optical microscopy with a hot stage. The alloys with higher propylene contents exhibited a faster spherulitic growth rate. The fold surface free energy was derived, and it was found that a large amount of block copolymer fractions and random copolymer fractions could reduce the fold surface free energy. The structure of the alloys also affected the crystallization regime of PP. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 632–638, 2005     

Characterization of reworkable high-temperature adhesives for MCM-D application

The need to have a high-temperature adhesive that can withstand temperatures in excess of 350°C for MCM-D silicon substrate process application, yet which can be reworkable at slightly high temperature ∼ 400°C for the removal from the glass pallet, is important. A novel, reworkable, high-temperature adhesive based on polyimide–amide–epoxy (PIAE) copolymer was developed and investigated using modulated differential scanning calorimetry (MDSC), thermal gravimetric analysis (TGA), Fourier Transform Infrared Spectroscopy (FTIR) and solid-probe pyrolysis mass spectroscopy (MS). Compared with commercial polyimide–amide (PIA) adhesives, FTIR spectra reveal that the thermally degradative ester groups contribute to the reworkability of the PIAE adhesive at a specific temperature (400°C), yet they remain thermally stable at a lower working temperature (350°C). FTIR spectrum comparison of the residuals of PIAE and PIA are similar after exposure to 400°C. MS spectra of outgassed products identify that the components of radical fragmentation from PIAE are due to polymeric chain degradation at 400°C, while only volatile trace water and N-methyl pyrolidone (NMP) are evolved from the commercial PIA adhesive. TGA results suggest a complementary explanation for the variation of total ion current (TIC) curves on these two adhesives. MDSC curves further verify that the reworkable PIAE adhesive is a copolymer. Furthermore, a reasonable thermal degradation mechanism is presented on the adhesive reworkability. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 997–1005, 1999     

Melt polymerization of copoly(ethylene terephthalate–imide)s and thermal properties

Copoly(ethylene terephthalate–imide)s (PETI) were prepared by melt polycondensation of bis(2-hydroxyethyl)terephthalate (BHET) and imide containing oligomer, i.e., 4,4′-bis[(4-carbo-2-hydroxyethoxy)phthalimido]diphenylmethane(BHEI). The apparent rate of poly-condensation reaction was faster than that of homo poly(ethylene terephthalate) (PET) due to the presence of imide units. The PETI copolymers with up to 10 mol % of BHEI unit in the copolymer showed about the same molecular weight and carboxyl end group content as homo PET prepared under similar reaction conditions. The increase in T_g of copolymer was more dependent on molar substitution of BHEI than on substitution of BHEN, reaching 91°C with 8 mol % BHEI units in the copolymer from T_g = 78.9°C of homo PET. In the case of PETN copolymer, 32 mol % of bis(2-Hydroxyethyl)naphthalate (BHEN) units gave T_g of 90°C. The maximum decomposition temperature of PETI copolymer was about the same as that of homo PET by TGA analysis. The char yield at 800°C was higher than that of homo PET. © 1996 John Wiley & Sons, Inc.     

Alternating copolymerization of methyl α-phenylacrylate and methyl methacrylate by n-BuLi

The copolymerization of methyl α-phenylacrylate (MPhA) and methyl methacrylate by n-BuLi was carried out in toluene at various temperatures with an initial monomer ratio of 1:1. At ?78°C the product was a homopolymer of MPhA. The copolymer obtained at ?40°C was a mixture of poly(methyl α-phenylacrylate) and poly(methyl methacrylate) containing a small amount of alternating copolymer of both monomers. With further increase in the polymerization temperature the fraction of alternating copolymer increased and above 30°C all the copolymers obtained were alternate. With varying composition of feed monomers the copolymerization was carried out at 30°C and the alternating copolymer was obtained over a wide range of monomer feed ratios. In tetrahydrofuran the alternate sequence began to form at a lower temperature than in toluene, and all the copolymers obtained above 0°C were alternating ones. The mechanism of the copolymerization is discussed in some detail.     

Copolymerization of carbon dioxide and propylene oxide using zinc adipate as catalyst

Zinc adipate was synthesized from zinc oxide with adipic acid by different methods. Their chemical structure and crystalline morphology were determined by Fourier transform infrared spectroscopy (FTIR), wide‐angle X‐ray diffraction (WXRD), and scanning electron microscopy (SEM) techniques. The results showed that the zinc adipate synthesized under magnetic stirring possessed higher degree of crystallinity than that synthesized under mechanical stirring due to the different stirring strength, and therefore exhibited greater catalytic activity for the copolymerization between CO₂ and propylene oxide (PO). The optimum condition for the copolymerization of CO₂ and PO was also investigated. Very high catalytic activity of 110.4 g polymer/g catalyst was afforded under optimizing copolymerization condition. NMR spectra revealed that the synthesized poly(propylene carbonate) (PPC) had a highly alternating copolymer structure. DSC and TGA examinations showed that the glass transition temperature and decomposition temperature of the PPC with M_n = 41,900 Da were 27.7 and 248°C, respectively. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 200–206, 2006     

Physical and chemical properties of methyl trifluoroacrylate–α-olefin copolymer and its hydrolyzed copolymer

Physical and chemical properties of alternating copolymers of methyl α,β,β-trifluoroacrylate (MTFA; CF₂?CFCO₂CH₃) with α-olefins such as ethylene, propylene, and isobutylene and their hydrolyzed copolymers were investigated. The original ester-type copolymers are amorphous and hydrophobic. The copolymers, except for the MTFA–isobutylene copolymer, were found to be easily hydrolyzed in boiled NaOH–methanol aqueous solution to give hydrophilic fluoropolymers which contain nearly theoretical amounts of carboxyl groups. No chain scission takes place during the hydrolysis. The decomposition temperature of the original ester-type copolymers is in the range of 347° to 379°C in nitrogen atmosphere, and the glass transition temperature is in the range of 21° to 76°C. Two steps of weight decrease, at around 100°C due to the removal of absorbed water and around 250°C due to the decomposition, were observed in the TGA curve of the hydrolyzed acid-type copolymers. Both ester- and acid-type copolymers were crosslinked by electron beam irradiation, while the MTFA–isobutylene copolymer was degraded. The tensile strength of the copolymers is in the range of 190 to 450 kg/cm².     

Synthesis,characterization, and electro‐optical properties of a soluble conjugated polymer containing an oxadiazole unit in the main chain

A novel copolymer, poly{[2,5‐diphenylene‐1,3,4‐oxadiazole‐vinylene]‐alt‐[2‐methoxy‐5‐(2‐ethylhexyloxy)‐1,4‐phenylenevinylene]}(MEH‐OPPV) containing a high‐electron‐affinity unit of aromatic oxadiazole in the main chain is synthesized through the Wittig condensation reaction. The obtained copolymer is easily soluble in conventional organic solvents. The structure of the copolymer was characterized by Fourier transform infrared, ¹H nuclear magnetic resonance, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and ultraviolet‐visible and photoluminescence spectroscopy. The TGA result indicates that the copolymer has very high thermal stability (stable up to 310°C in nitrogen), while DSC investigation demonstrates that the glass transition temperature (T_g) is 143°C, which might be a merit for the long‐life operation of light‐emitting devices. The absorption spectrum of film sample of the copolymer reveals two peaks at 310 and 370 nm, respectively, and the edge absorption corresponds to a band gap of 2.46 eV. A single‐layer light‐emitting diode device ITO/MEH‐OPPV/Al is successfully fabricated. The device emits visible yellowish‐green light above the bias voltage of 4.0 V under ambient condition. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2618–2623, 2003     

Study on thermal behavior of impact polypropylene copolymer and its fractions

An impact polypropylene copolymer (IPC) was fractionated into three fractions using n‐octane as solvent by means of temperature‐gradient extraction fractionation. The glass transitions, melting, and crystallization behavior of these three fractions were studied by modulated differential scanning calorimeter (MDSC) and wide‐angle X‐ray diffraction (WAXD). In addition, successive self‐nucleation and annealing (SSA) technique was adopted to further examine the heterogeneity and the structure of its fractions. The results reveal that the 50°C fraction (F₅₀) mainly consists of ethylene‐propylene random copolymer and the molecular chains may contain a few of short but crystallizable propylene and/or ethylene unit sequences; moreover, the lamellae thicknesses of the resulting crystals are extremely low. Furthermore, 100°C fraction (F₁₀₀) mainly consist of some branched polyethylene and various ethylene‐propylene block copolymers in which some ethylene and propylene units also randomly arrange in certain segments, and some polypropylene segments can form crystals with various lamellae thickness. An obvious thermal fractionation effect for F₁₀₀ samples after being treated by SSA process is ascribed to the irregular and nonuniform arrangement of ethylene and propylene segments. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Effect of Processing Conditions on Styrene-Butadiene-Styrene-Thermoplastic Rubber

The effects of shear rate, extrusion temperature and heat treatment on a lamellar triblock copolymer of styrene-butadiene-styrene were studied using extrudates from a capillary rheometer. The rheological behaviour is mainly non-Newtonian in the region studied and the flow curves can be time-temperature reduced. The quality of the domain structure PS phase was measured mechanically in terms of the stress at yield and optically by birefringence. Some of the factors considered during the analysis of the results are: rearrangement of the imperfect original domain structure taking place in the barrel, before extrusion, for temperatures higher than 145°C; partial destruction of this pre-developed structure during extrusion; orientation of the chains during extrusion and under some conditions, the development of sharkskin on the surface of the extrudate. The heat treatment induces the copolymer to undergo three processes: internal stress relaxation (～135°C); rearrangement of the imperfect domain structure (145°CT240°C); and crosslinking in the rubbery phase (T200°C).     

Melt flow indexer evidence of high‐temperature transitions in molten high‐density polyethylenes

A melt flow indexer (MFI) was used to investigate high‐temperature transitions in melts of high‐density polyethylene (HDPE). The MFI data were obtained in the range 190–230°C. These transitions were found in the MFI at about 210 and 225°C and reproduced in a Haake melt blender. Polystyrene was used in the blender experiment to demonstrate typical amorphous behavior. For HDPE melts, the MFI–temperature behavior and the torque–temperature data of the blender were found to be alternative images of the same anomalous temperature dependency in the range 210–225°C. Also, the Haake melt blender was able to reproduce the 150°C transition observed by Kolnaar and Keller in the extrusion of HDPE. Regardless of the simplicity of the MFI device, results are in agreement with our previous DSC findings. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1309–1313, 2004     

Blends of SBS triblock copolymer with poly(2,6‐dimethyl‐1,4‐phenylene oxide)/polystyrene mixture

Blends of styrene–butadiene–styrene (SBS) or styrene–ethylene/1‐butene–styrene (SEBS) triblock copolymers with a commercial mixture of polystyrene (PS) and poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO) were prepared in the melt at different temperatures according to the chemical kind of the copolymer. Although solution‐cast SBS/PPO and SBS/PS blends were already known in the literature, a general and systematic study of the miscibility of the PS/PPO blend with a styrene‐based triblock copolymer in the melt was still missing. The thermal and mechanical behavior of SBS/(PPO/PS) blends was investigated by means of DSC and dynamic thermomechanical analysis (DMTA). The results were then compared to analogous SEBS/(PPO/PS) blends, for which the presence of a saturated olefinic block allowed processing at higher temperatures (220°C instead of 180°C). All the blends were further characterized by SEM and TGA to tentatively relate the observed properties with the blends' morphology and degradation temperature. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2698–2705, 2003     

Alternating copolymerization of butadiene and propylene

An alternating copolymer of propylene and butadiene is prepared with vanadium or titanium compounds and alkylaluminum compounds as the polymerization catalyst. The catalyst should be prepared at extremely low temperature as?70°C and halogen atom is essential to the catalyst activity. Carbonyl compounds such as ketone, acid, ester, acid anhydride, and acid peroxide are very effective additives to the catalyst for enhancement of the molecular weight of the polymer. The potentiometric titration and the ESR study suggest that a divalent vanadium compound associated to form the dimer through chlorine bridge is a precursor of the active species. An anionic copolymerization mechanism involving the alternating coordination of monomers is proposed. The copolymer is always of a 1 : 1 composition irrespective of the composition of monomer feed and the alternating structure of polypropylene and trans-1,4-polybutadiene is estimated from IR and NMR data. The copolymer seems to be a new versatile synthetic rubber having excellent low temperature properties, high rebound, good compatibility with conventional rubbers and high resistance toward aging.     

Viscoelastic behavior of chlorinated polyethylene/poly(ethylene‐co‐vinyl acetate) blends in the melt state

Blends of chlorinated polyethylene and an ethylene vinyl acetate copolymer of various compositions were prepared by mixing in the melt state. Dynamic rheological properties of these blends were studied at different temperatures below, near, and above the T_S, the temperature of phase separation, and in a frequency range from 0.01 to 100 rad/s. It is shown that the time–temperature superposition principle is suitable in all investigated temperature ranges. G′ versus G″ representations for the blends were found to be independent of temperature and varying weakly with the composition. Changes in the relaxation spectra H(τ) were discovered which depend on the prehistory of the blend preparation and on thermal conditions in the working unit of a rheometer (increasing the temperature from 140 to 180°C or decreasing the temperature from 180 to 140°C). © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1911–1918, 2003     

Elongation properties of polyethylene melts

The extensional rheological properties of three grades of polyethylene melts, low density polyethylene (LDPE), linear low density polyethylene (LLDPE), and high density polyethylene (HDPE) were measured using a melt spinning technique under the test conditions with temperature ranging from 150 to 210°C and extrusion rate varying from 11.25 to 22.50 mm s^?1. The results showed that the melt strength decreased with a rise of temperature while increased with an increase of extensional rate. With the rise of extensional strain rate and temperature, the melt extensional viscosity decreased. The extensional stress and viscosity reduced with increasing extrusion velocity when the temperature and extensional rate were constant. Moreover, the melt strength and extensional viscosity of the LDPE resin was the highest and the LLDPE was the lowest under the same experimental conditions. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

Free radical branching of polylactide by reactive extrusion

The reactive extrusion of polylactide (PLA) with a free radical initiator resulting in a branched polymer was accomplished. Reaction conditions were in the range of 160°C to 200°C with an initiator concentration between 0.0 and 0.5%. Triple detector size exclusion chromatography, melt flow index, thermal gravimetric analysis, differential scanning calorimetry, and dynamic mechanical analysis were used to characterize the polylactide polymers. PLA without initiator showed extensive degradation as was evidenced by a decrease in both molecular weight and melt viscosity. The optimum range for branching resulting in a high molecular weight and low melt flow index polylactide was found to be around 170°C to 180°C and 0.1 to 0.25% initiator.     

EVA–EPDM blends as cable insulant

Base materials for heat-resistant cable insulant have been developed from blends of ethylene vinyl acetate (EVA) copolymer containing 28% VA and ethylene propylene diene (EPDM) rubber. Different electrical, mechanical, and thermal properties of these blends have been studied extensively. Aging under different conditions has also been studied. The chemical and mechanical stability of these compositions has been assessed at the actual temperature range of application. Dielectric properties have been determined against varying temperature. These blends may be used as insulating materials having a temperature rating around 90–130°C, which is above the temperature rating (85–90°C) of heat-resistant insulation based on EPDM. © 1994 John Wiley & Sons, Inc.     

Improved thermal stability and mechanical properties of poly(propylene carbonate) by reactive blending with maleic anhydride

To extend the application of a carbon dioxide sourced environmental friendly polymer: poly (propylene carbonate) (PPC), a small amount of maleic anhydride (MA) was melt blended to end‐cap with PPC to improve its thermal stability and mechanical properties. Thermal and mechanical properties of end‐capped PPC were investigated by TGA, GPC, mechanical test, and DMA. TGA and titration results demonstrate that PPC can be easily end‐capped with MA through simple melt blending. TGA results show that the thermal degradation temperature of PPC could be improved by around 140°C by adding MA. GPC measurement indicates that the molecular weight of PPC can be maintained after blending with MA, where pure PPC experiences a dramatic degradation in molecular weight during melt process. More importantly, the tensile strength of PPC after blending with MA was found to be nearly eight times higher than that of pure PPC. It has approached the mechanical properties of polyolefin polymers, indicating the possibility of replacing polyolefin polymers with PPC for low temperature applications. The method described here could be used to extend the applications of PPC and fight against the well known global warming problem. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synthesis and properties of aliphatic polycarbonates derived from carbon dioxide,propylene oxide and maleic anhydride

Terpolymerization of carbon dioxide (CO₂) with propylene oxide (PO) and maleic anhydride (MA) was successfully carried out using supported zinc glutarate catalyst. Consequently giving high molecular weight poly(propylene carbonate maleate) (PPCMA) in a very high yield (72.5 g polymer/g catalyst). The resulting terpolymers were fully characterized by FTIR, ¹H NMR, ¹³C NMR, and wide‐angle X‐ray diffraction (WAXD) techniques. NMR measurements showed that PPCMA had an almost alternating structure for the components of carbon dioxide and PO. The influence of molecular weight and MA content on the properties of PPCMA was also investigated. Differential scanning calorimetry (DSC) measurements revealed that the glass transition temperature (T_g) of PPCMA increased with increasing molecular weight. Thermogravimetric analysis (TGA) indicated that PPCMA51 exhibited a very high decomposition temperature (263°C) due to the introduction of the double bond of MA into the backbone of terpolymer. The terpolymers with double bonds can be readily subjected to crosslinking reaction in high temperature to give a slightly crosslinked PPCMA, which exhibit superior thermal stability. Tensile tests also showed that the mechanical properties of PPCMA increased with increasing molecular weight. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008