聚氯乙烯-丙烯酸丁酯接枝共聚物的结构表征

以通用聚氯乙烯(PVC)和脱氯化氢PVC树脂为基体,采用悬浮溶胀接枝共聚法合成聚氯乙烯-丙烯酸丁酯接枝共聚物,对脱氯化氢PVC和接枝共聚物的结构进行了表征.结果表明,以碱液为介质加热PVC能脱除少量氯化氢,得到以链节数为2,3,4的共轭双键为主的不饱和结构,而树脂的分子量变化不大;在相同接枝反应条件下,采用脱氯化氢PVC与丙烯酸丁酯接枝共聚可以提高接枝率和接枝效率;PVC接枝共聚物的特性粘度随接枝率增加而增加,其重均分子量和分子量分布指数均大于接枝所用的PVC树脂.     

Photodehydrochlorination of carbon monoxide–vinyl chloride copolymer

In order to examine effect of the carbonyl group in carbon monoxide–vinyl chloride copolymer, poly(CO–VC), photoirradiation with a high-pressure mercury lamp on the copolymer was carried out. Poly(CO–VC) had a rate of dehydrochlorination three times that of PVC, and the reaction involved a decrease in chlorine content. Also there was a marked change in the ultraviolet spectra of the photoirradiated films. However, no pronounced change of molecular weight was observed, but a change in R_f in TLC was observed clearly. These facts confirmed that photoirradiation of poly(CO–VC) produced a structural change by dehydrochlorination without serious decrease of molecular weight. In addition, photodehydrochlorination of the copolymer or PVC film was followed kinetically, and after ozonolysis of the dehydrochlorinated polymers, the number-average molecular weights were measured. From the results of degree of dehydrochlorination and molecular weight, the number average of conjugated double bonds or carbonyl groups was estimated. A mechanism for dehydrochlorination process by photo-irradiation is suggested.     

New routes for copolymerization of carbon monoxide with styrene or vinyl chloride and photodegradation of these copolymers in solutions

New routes for copolymerization of carbon monoxide with styrene or vinyl chloride were found by emulsion polymerization (nonionic or ionic emulsifier). These procedures yielded copolymers containing carbonyl groups even at high conversion. These carbonyl-containing polyketones were photoirradiated in solvent. In carbon monoxide—styrene copolymer of high molecular weight, the viscosity change produced by photoirradiation was especially remarkable, while in carbon monoxide—vinyl chloride copolymer no pronounced change in viscosity was observed, even at high contents of carbonyl group.     

Preparation and characterization of novel thermal-stable vinylidene chloride–methyl acrylate–glycidyl methacrylate copolymer

A novel copolymer was synthesized by vinylidene chloride (VDC)/methyl acrylate (MA)/glycidyl methacrylate (GMA). The Fourier transform infrared (FTIR) and ¹H-nuclear magnetic resonance analyses indicated that the copolymer of VDC/MA/GMA (PVMG) was synthesized successfully. The influences of GMA on the molecular weight, melting point, and thermal stability of copolymer were investigated by gel permeation chromatograph, differential scanning calorimeter, thermogravimetric analysis–FTIR, respectively. The copolymerization eliminated the phenomenon of “double melting peaks” for poly(vinylidene chloride), and the melting point was reduced to 165°C. The GMA also enhanced the thermal stability of copolymer, which was proved by the increased decomposition temperature of copolymer. The existence of GMA caused the cross-linking of the copolymer, which contributed to the improvement of barrier performance of PVMG.     

Synthesis and characterization of graft copolymers of poly(vinyl chloride) with styrene and (meth)acrylates by atom transfer radical polymerization

Graft copolymers of poly(vinyl chloride) with styrene and (meth)acrylates were prepared by atom transfer radical polymerization. Poly(vinyl chloride) containing small amount of pendent chloroacetate units was used as a macroinitiator. The formation of the graft copolymer was confirmed with size exclusion chromatography (SEC), ¹H NMR and IR spectroscopy. The graft copolymers with increasing incorporation of butyl acrylate result in an increase of molecular weight. One glass transition temperature (T_g) was observed for all copolymers. T_g of the copolymer with butyl acrylate decreases with increasing content of butyl acrylate.     

Influence of physical-chemical interactions on the thermal stability and surface properties of poly(vinyl chloride)-b-poly(hydroxypropyl acrylate)-b-poly(vinyl chloride) block copolymers

The synthesis of poly(vinyl chloride) (PVC) homopolymers and poly(vinyl chloride)-b-poly(hydroxypropyl acrylate)-b-poly(vinyl chloride) (PVC-b-PHPA-b-PVC) block copolymers via a single electron - degenerative transfer mediated living radical polymerisation was carried out on a pilot scale in industrial facilities. The thermal stability of the products was assessed conductimetrically. The block copolymers, that contained a low content of PHPA (below 12 wt.%), showed thermal stability that was approximately three times greater than that of conventional PVC. Inverse gas chromatography study of the copolymers surface showed that there was a decrease in the dispersive component and greater Lewis acidity and basicity constants were observed relative to those of PVC. The thermal stabilisation of PVC when in the presence of PHPA is explained by the interactions between its functional groups and the structures formed during the thermal degradation. The thermal stability and the surface properties of PVC-b-PHPA-b-PVC were strongly dependent on the molecular weight of the block copolymer. Lewis acid-base interaction parameters were determined and are interpreted as evidence of the PVC-b-PHPA-b-PVC compatibilising function in PVC-wood flour composites.     

MCM-41分子筛负载氯化铝催化丙烯酸甲酯与1-辛烯共聚

以MCM-41分子筛负载氯化铝为催化剂, 催化丙烯酸甲酯与1-辛烯共聚合反应, 利用称重法测定聚合物产率, 利用核磁共振氢谱分析共聚物组成, 利用凝胶渗透色谱分析共聚物相对数均分子质量, 研究了聚合物产率和共聚物组成随聚合反应时间的变化规律, 考察了溶剂、 催化剂组成和催化剂用量对共聚合结果的影响及催化剂的循环使用性能. 结果表明, 聚合物产率随时间呈S形增长, 而共聚物组成随时间保持恒定, 与氯化铝催化体系规律一致; 溶剂由二氯甲烷改变为乙醇或二甲苯主要影响聚合物组成, 对聚合物相对数均分子质量及其分布影响不大; 催化剂中活性组分的增加有利于增加共聚物中1-辛烯单元的含量, 但对聚合物分子量及分子量分布影响不大; 催化剂中活性组分含量一定时, 随催化剂与单体摩尔比从0.125增加到0.5, 共聚物中1-辛烯单元含量增加, 继续增大催化剂用量不利于提高共聚物中1-辛烯单元含量. 催化剂重复使用3次后仍具有良好的催化活性, 将烯烃单元引入共聚物中, 获得1-辛烯单元摩尔分数达30.1%的聚(丙烯酸甲酯-co-1-辛烯)共聚物.     

Macromolecular models for branched PVC. I. Copolymer of vinyl chloride with isopropenyl chloride

A new type of model for study of polymer anomalies by copolymerization is proposed. For branched PVC, the vinyl chloride–isopropenyl chloride copolymer was used as the macromolecular model. A regulatory and inhibitory action of isopropenyl chloride during the polymerization was demonstrated. To determine the composition of the copolymer, methods based on elemental analysis and NMR and infrared spectra were utilized. It was found that the copolymer composition is very close to that of the polymerization mixture. The structure of the copolymer was studied from infrared spectra. It was found that both forms T_CHH and T_HHH are present, the former being present in a larger quantity. The possibility of the utilization of spectral methods on macromolecular systems to determine the structure and content of a chlorine atom bound to a tertiary carbon atom (Cl_T) in the presence of an excess of chlorine bound to a secondary carbon was verified.     

Grafting of Polystyrene-b-Poly(2-hydroxyethyl methacrylate) onto Carbon Fiber

Carbon fiber (CF) was subjected to oxidation and acyl chlorination, resulting in CF functionalized with acyl chloride (CF-COCl). The block copolymer polystyrene-b-poly (2-hydroxyethyl methacrylate) (PSt-b-PHEMA) was synthesized by atom-transfer radical polymerization (ATRP). According to the reaction between hydroxyl groups of block copolymer and acyl chloride groups on CF, the block copolymer was successfully grafted onto the surface of CF. Fourier-transform infrared spectra (FTIR), Gel permeation chromatography (GPC) were used to determine the chemical structure and molecular weight of block copolymer; Fourier transform infrared spectroscopy-attenuated total reflection (FTIR-ATR), Scanning electron microscopy (SEM) and thermal gravimetric analyses (TGA) were used to determine the chemical property and structure of grafted CF.     

A study of molecular weight of methyl methacrylate–styrene copolymer

An alternating copolymer of methyl methacrylate and styrene was obtained by the reaction of these two monomers in the aqueous phase and in presence of zinc chloride acting as complexing agent. It was found that the optimum conditions were obtained when the monomer concentrations are equal. The molecular weight and the molecular weight distribution were obtained by gel permeation chromatography (GPC). The polymers obtained have a very narrow molecular weight distribution. A model which takes into account the various parameters is proposed.     

Dispersion copolymerization of acrylamide with quaternary ammonium cationic monomer in aqueous salts solution

Dispersion copolymerization of acrylamide (AM) with 2-methylacryloylxyethyl trimethyl ammonium chloride (DMC) has been carried out in aqueous salts solution containing ammonium sulfate and sodium chloride with poly(acryloylxyethyl trimethyl ammonium chloride) (PDAC) as the stabilizer and 2,2′-azobis[2-(2-inidazolin-2-yl)propane]-dihydro chloride (VA-044) as the initiator. A new particle formation mechanism of the dispersion polymerization for the present system has been proposed. The effects of inorganic salts and stabilizer concentration on dispersion polymerization have been investigated. The results show that varying the salt concentration could affect the morphology and molecular weight of the resultant copolymer particles significantly. With increasing the stabilizer concentration, the particle size decreased at first and then increased, meanwhile the effect on the copolymer molecular weight was the contrary. These results had been rationalized based on the proposed mechanism.     

Thermal stability of poly(acryloyl chloride) homopolymer and copolymers of acryloyl chloride with methyl methacrylate

The thermal stabilities of poly(acryloyl chloride) homopolymer and copolymers of acryloyl chloride with methyl methacrylate covering the entire composition range were studied by thermogravimetric analysis. At each extreme of the composition range incorporation of comonomer units results in a copolymer which is less stable than the PMMA homopolymer. The activation energies of the decomposition of the copolymers were calculated using the Arrhenius equation and found to decrease from 32.2 to 12.5 kJ mol^?1 as acryloyl chloride concentration of the copolymer increases, indicating that the copolymers of higher acryloyl chloride concentration should easier decompose than other copolymers. The reactivity ratios of the copolymer were calculated and found to ber ₁(AC)=0.2±0.02 andr ₂(MMA)=0.9±0.1.     

γ-Ray-induced copolymerization of ethylene and vinyl chloride in liquid carbon dioxide

The γ-ray-induced copolymerization of ethylene and vinyl chloride with the use of liquid carbon dioxide as a solvent was studied under a total pressure of 400 kg/cm², with a dose rate of 2.5 × 10⁴ rad/hr at 30°C. A rubberlike, sticky polymer is obtained when the molar concentration of vinyl chloride is less than 30% in the monomer mixture, and the polymer is a white powder at higher concentrations of vinyl chloride. Infrared, x-ray, and differential thermal analyses confirm that the polymerization products are noncrystalline, true random copolymers. The rate of copolymerization decreases markedly when a small amount of vinyl chloride is added to ethylene monomer. In the range of vinyl chloride concentration higher than 5%, however, the rate and the molecular weight of copolymer increase with increasing concentration of vinyl chloride. It has been concluded from kinetic considerations based on these results that the rate of initiation increases proportionally with the concentration of vinyl chloride. Further, the growing chain radicals are shown to be deactivated by the cross-termination reaction between the radicals with terminal unit of ethylene and vinyl chloride, and no transfer reaction occurs.     

Linear polybenzyls. III. Sterically assisted linear polymerization of 2,5-dimethylbenzyl chloride and α-methylbenzyl chloride

The low-temperature Friedel-Crafts step-growth polymerization reactions of 2,5-dimethylbenzyl chloride with TiCl₄—(C₂H₅)₂AlCl catalyst, and of α-methylbenzyl chloride with AlCl₃ catalyst were investigated for the effect of reaction conditions on polymer molecular weight, linearity, glass transition temperature, and crystalline properties. Premature precipitation of highly crystalline poly(2,5-dimethylbenzyl) prevented the preparation of high molecular weight products from this monomer, while most likely an indanyl-type termination reaction limited the molecular weight of poly(α-methylbenzyl). Model reactions indicated that, under proper conditions, the latter could be prepared with 99% para substitution, and these polymers were crystalline.     

Polyelectrolyte complexes of linear copolymers and hydrogels based on 2‐[(methacryloyloxy)ethyl]trimethylammonium chloride and N‐isopropylacrylamide

The formation of polyelectrolyte complexes of linear copolymers and hydrogels based on copolymers of 2‐[(methacryloyloxy)ethyl]trimethylammonium chloride with N‐isopropylacrylamide (MADQUAT–NIPAAM) and poly(acrylic acid) (PAA) has been studied. The composition of the copolymer has been found to affect the composition of the polyelectrolyte complexes significantly, and the molecular weight of PAA influences their aggregation stability. Hydrogels of MADQUAT–NIPAAM immersed in solutions of PAA undergo contraction because of the formation of gel–polymer complexes. The rate of contraction and the final swelling degree of the gel–polymer complexes depend on the concentration of PAA in solution and its molecular weight. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1506–1513, 2004     

Grafting of polymethyl methacrylate from poly(ethylene-co-vinylacetate) copolymer using atom transfer radical polymerization

Atom transfer radical polymerization was employed for the first time to prepare graft copolymer having by ethylene-vinyl acetate (EVA) copolymer as backbone and poly(methyl methacrylate) (PMMA) as branches. The polymerization of MMA was initiated by EVA carrying chloropropionate groups as macroinitiator, in the presence of copper chloride (CuCl) and bipyridine (bpy) at 80 °C. The macroinitiator was prepared by esterification of partially hydrolyzed EVA with 2-chloropropionyl chloride. Successful graft copolymerizations were performed both in toluene/γ-butyrolactone mixed solvent and in toluene solution, with grafting efficiency of 12% and 6%, respectively. Molecular weight distribution of the PMMA segments around 1.2 has been achieved with pure toluene solution. The ATRP graft copolymerization was supported by an increase of the molecular weight of the graft copolymers, as compared to that of the macroinitiator and also by their monomodal molecular weight distribution.     

Grafting of polymers onto a carbon‐fiber surface by ligand‐exchange reaction of poly(vinyl ferrocene‐co‐vinyl monomer) with polycondensed aromatic rings of the surface

To improve the surface of carbon fiber, the grafting reaction of copolymer containing vinyl ferrocene (VFE) onto a carbon‐fiber surface by a ligand‐exchange reaction between ferrocene moieties of the copolymer and polycondensed aromatic rings of carbon fiber was investigated. The copolymer containing VFE was prepared by the radical copolymerization of VFE with vinyl monomers, such as methyl methacrylate (MMA) and styrene, using 2,2′‐azobisisobutyronitrile as an initiator. By heating the carbon fiber with poly(VFE‐co‐MMA) (number‐average molecular weight: 2.1 × 10⁴) in the presence of aluminum chloride and aluminum powder, the copolymer was grafted onto the surface. The percentage of grafting reached 46.1%. On the contrary, in the absence of aluminum chloride, no grafting of the copolymer was observed. Therefore, it is considered that the copolymer was grafted onto the carbon‐fiber surface by a ligand‐exchange reaction between ferrocene moieties of the copolymer and polycondensed aromatic rings of carbon fiber. The molar number of grafted polymer chain on the carbon‐fiber surface decreased with increasing molecular weight of poly(VFE‐co‐MMA) because the steric hindrance of grafted copolymer on the carbon‐fiber surface increases with increasing molecular weight of poly(VFE‐co‐MMA). © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1868–1875, 2002     

Methyl methacrylate-n-butyl methacrylate copolymer containing ferric chloride: Mössbauer study

Methyl methacrylate /MMA/-n-butyl methacrylate /nBuMA/ copolymer containing anhydrous ferric chloride was prepared by free radical polymerization at 70 °C. TGA studies showed that the addition of ferric chloride increases the thermal stability of copolymer by 90 °C. Mössbauer studies of the copolymer were carried out to determine the oxidation state and environments of iron in the copolymer. Mössbauer studies of the copolymer heated at 150 °C, 300 °C and 500 °C for 1 h showed that during the thermal degradation, no reduction of Fe³⁺ takes place.     

Synthesis of poly(vinyl chloride)‐b‐poly(n‐butyl acrylate)‐b‐poly(vinyl chloride) by the competitive single‐electron‐transfer/degenerative‐chain‐transfer‐mediated living radical polymerization in water

The synthesis of a block copolymer poly(vinyl chloride)‐b‐poly(n‐butyl acrylate)‐b‐poly(vinyl chloride) is reported. This new material was synthesized by single‐electron‐transfer/degenerative‐chain‐transfer‐mediated living radical polymerization (SET‐DTLRP) in two steps. First, a bifunctional macroinitiator of α,ω‐di(iodo)poly (butyl acrylate) [α,ω‐di(iodo)PBA] was synthesized by SET‐DTLRP in water at 25 °C. The macroinitiator was further reinitiated by SET‐DTLRP, leading to the formation of the desired product. This ABA block copolymer was synthesized with high initiator efficiency. The kinetics of the copolymerization reaction was studied for two PBA macroinitiators with number–average molecular weight of 10 k and 20 k. The relationship between the conversion and the number–average molecular weight was found to be linear. The dynamic mechanical thermal analysis suggests just one phase, indicating that copolymer behaves as a single material with no phase separation. This methodology provides the access to several block copolymers and other complex architectures that result from combinations of thermoplastics (PVC) and elastomers (PBA). From industrial standpoint, this process is attractive, because of easy experimental setup and the environmental friendly reaction medium. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3001–3008, 2006     

KINETICS OF VINYL CHLORIDE (CO) POLYMERIZATION AT HIGH CONVERSION

This paper provides a summarized review on the kinetics of vinyl chloride homopolymerization inthe absence and presence of chain transfer agents, of VC/DAP(diallyl phthalate) copolymerization with chainextension and/or slightly crosslinking functions, and of vinylidene chloride/VC random copolymerization.Models of rate, degree of polymerization or molecular weight, copolymer composition, gel fraction andcrosslinking density were proposed and interpreted mechanistically.