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1.
To accelerate the living radical polymerization (LRP) of vinyl chloride (VC) in water the phase transfer catalyzed single electron transfer–degenerative chain transfer mediated living radical polymerization (SET–DTLRP) of VC mediated by sodium dithionite (Na2S2O4) was investigated. The fastest polymerization reaction that still produces thermally stable poly(vinyl chloride) (PVC) takes place at 43 °C with the ratio [PTC]0/[Na2S2O4]0 = 0.0075/1. Cetyltrimethylammonium bromide (nC16H33(CH3)3N+Br?, CetMe3NBr) was the phase‐transfer catalyst (PTC) of choice. Under these conditions the first, fast stage of SET–DTLRP of VC was accomplished within 7–8 h when the initial ratio monomer/initiator [VC]0/[CHI3]0 was 800. The number‐average molecular weight (Mn) of the resulting PVC was in good agreement with the theoretical molecular weight (Mth). When the [VC]0/[CHI3]0 ratio was 4800, the fast step of the reaction was accomplished within 17 h, to produce 72% monomer conversion. A deviation of the Mn from the Mth was observed in this case. Possible mechanistic explanations for this deviation as well as for the phase transfer catalyzed SET–DTLRP of VC were suggested. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 779–788, 2005  相似文献   

2.
Poly(viny1 chloride) (PVC) was dehydrochlorinated thermally in pyridine solution under N2 atmosphere and the effect of variation of reaction time, temperature, and concentration of PVC in pyridine was studied. The extent of dehydrochlorination (or conversion, x%) increases with an increase in reaction time and temperature, and with a decrease in the concentration of PVC. Incomplete precipitation of dehydrochlorinated PVC (DHPVC) occurs by nonsolvent (methanol). During dehydrochlorination there is no HCl evolution as it forms a pyridine hydrochloride complex which is supposed to act as a catalyst for dehydrochlorination. A possible mechanism has been proposed. Chain scission and cross-linking reactions are responsible for the molecular weight changes that take place during the reaction.  相似文献   

3.
A tetrahydrofuran (THF) solution of the living random copolymer of methyl methacrylate (MMA) and glycidyl methacrylate (GMA) was prepared by the living anionic copolymerization of the two monomers, using 1,1‐diphenylhexyllithium (DPHLi) as initiator, in the presence of LiCl ([LiCl]/[DPHLi]0 = 3), at −50°C. The copolymer thus obtained has a controlled composition and molecular weight and a narrow molecular weight distribution. By introduction of an anionic living polystyrene (poly(St)) or anionic living polyisoprene (poly(Is)) solution into the above system at −30°C, a coupling reaction took place and a graft copolymer with a polar backbone and nonpolar side chains was produced. The solvent used in the preparation of the living poly(St) or poly(Is) affects the coupling reaction. When benzene was the solvent, a graft copolymer of high purity, controlled graft number and molecular weight, and narrow molecular weight distribution (Mw/Mn = 1.11–1.21) was obtained. In the coupling reaction, the living poly(St) reacted only with the epoxy groups and not with the carbonyls of the backbone polymer. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 105–112, 1999  相似文献   

4.
Thermal degradation of PVC treated with alkylaluminum compounds has been studied. Four PVC samples of different molecular weights have been treated with Me3Al, and Et3A1, and the dehydrochlorination rates of the polymers were determined at 190 and 220°C under a nitrogen atmosphere. The alkylaluminum-treated low molecular weight samples show marked increase in thermal stability, i. e., slower rate of dehydrochlorination right from the beginning of degradation, whereas with the higher molecular weight samples stabilization becomes pronounced only after a few percent of dehydrochlorination. The color of R3Al-treated samples was much lighter (yellowish) than those of controls (dark brown) at 1% HCl loss. The average polyene sequence lengths formed during the early stages of dehydrochlorination are found to be much shorter with RsAl-treated PVC than with virgin samples. It appears as though polyene sequences which arose by zipping- initiation from allylic and/or tertiary chlorine sites are longer than those which form by random initiation along the chain. The autocatalytic (i. e., HC1-catalyzed) dehydrochlorination observed with virgin PVC disappears after treatment with R3A1. The HCl-catalyzed dehydrochlorination is minimized when thin films are used instead of powdery samples, which may be due to higher rates of HC1 diffusion through thin films. Autocatalysis of dehydrochlorination is affected by the concentrations of double bonds and HCl and the length of polyene sequences. Interaction between polyenes and HC1 by hydrogen transfer may lead to the re-initiation of unzipping, thus lengthening the polyene sequences.  相似文献   

5.
Peroxidized polypropylene has been used as a heterofunctional initiator for a two-step emulsion polymerization of a vinyl monomer (M1) and vinyl chloride with the production of vinyl chloride block copolymers. Styrene, methyl-, and n-butyl methacrylate and methyl-, ethyl-, n-butyl-, and 2-ethyl-hexyl acrylate have been used as M1 and polymerized at 30–40°C. In the second step vinyl chloride was polymerized at 50°C. The range of chemical composition of the block copolymers depends on the rate of the first-step polymerization of M1 and the duration of the second step; e.g., with 2-ethyl-hexyl acrylate block copolymers could be obtained with a vinyl chloride content of 25–90%. The block copolymers have been submitted to precipitation fractionation and GPC analysis. Noteworthy is the absence of any significant amount of homopolymers, as well as poly(M1)n as PVC. The absence of homo-PVC was interpreted by an intra- and intermolecular tertiary hydrogen atom transfer from polypropylene residue to growing PVC sequences. The presence of saturated end groups on the PVC chains is responsible for the improved thermal stability of these block polymers, as well as their low rate of dehydrochlorination (180°C). Molecular aggregation in solution has been shown by molecular weight determination in benzene and tetrahydrofuran.  相似文献   

6.
The accelerated single electron transfer–degenerative chain transfer mediated living radical polymerization (SET–DTLRP) of vinyl chloride (VC) in H2O/tetrahydrofuran (THF) at 25 °C is reported. This process is catalyzed by sodium dithionite (Na2S2O4)‐sodium bicarbonate (NaHCO3). Electron transfer cocatalysts (ETC) 1,1′‐dialkyl‐4,4′‐bipyridinum dihalides or alkyl viologens were also employed in this polymerization. The resulting poly(vinyl chloride) (PVC) has a number‐average molecular weight (Mn) = 2,000–12,000, no detectable amounts of structural defects, and both active chloroiodomethyl and inactive chloromethyl chain ends. The molecular weight distribution of PVC obtained is Mw/Mn = 1.5. The surface active agents afford the final polymers as a powder and provide an acceleration of the rate of polymerization. The role of ETC is to accelerate the single electron transfer (SET) step, whereas THF enhances the degenerative chain transfer (DT) step. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 6364–6374, 2004  相似文献   

7.
Solution and aqueous miniemulsion polymerizations of vinyl chloride (VC) mediated by (3,3,4,4,5,5,6,6,7,7,8,8,8‐tridecafluorooctyl‐2‐((ethoxycarbonothioyl)thio) propanoate) (X1) were studied. The living characters of X1‐mediated solution and miniemulsion polymerizations of VC were confirmed by polymerization kinetics. The miniemulsion polymerization exhibits higher rate than solution polymerization. Final conversions of VC in the reversible addition‐fragmentation chain transfer (RAFT) miniemulsion polymerization reach as high as 87% and are independent of X1 concentration. Initiation process of X1‐mediated RAFT miniemulsion polymerization is controlled by the diffusion–adsorption process of prime radicals. Due to the heterogeneity of polymerization environments and concentration fluctuation of RAFT agent in droplets or latex particles, PVCs prepared in RAFT miniemulsion exhibit relatively broad molecular weight distribution. Furthermore, chain extensions of living PVC (PVC‐X) with VC, vinyl acetate (VAc), and N‐vinylpyrrolidone (NVP) reveal that PVC‐X can be reinitiated and extended, further confirming the living nature of VC RAFT polymerization. PVC‐b‐PVAc diblock copolymer is successfully synthesized by the chain extension of PVC‐X in RAFT miniemulsion polymerization. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 2092–2101  相似文献   

8.
A successive method for preparing novel amphiphilic graft copolymers with a hydrophilic backbone and hydrophobic side chains was developed. An anionic copolymerization of two bifunctional monomers, namely, allyl methacrylate (AMA) and a small amount of glycidyl methacrylate (GMA), was carried out in tetrahydrofuran (THF) with 1,1‐diphenylhexyllithium (DPHL) as the initiator in the presence of LiCl ([LiCl]/[DPHL]0 = 2), at −50 °C. The copolymer poly(AMA‐co‐GMA) thus obtained possessed a controlled molecular weight and a narrow molecular weight distribution (Mw /Mn = 1.08–1.17). Without termination and polymer separation, a coupling reaction between the epoxy groups of this copolymer and anionic living polystyrene [poly(St)] at −40 °C generated a graft copolymer with a poly(AMA‐co‐GMA) backbone and poly(St) side chains. This graft copolymer was free of its precursors, and its molecular weight as well as its composition could be well controlled. To the completed coupling reaction solution, a THF solution of 9‐borabicyclo[3.3.1]nonane was added, and this was followed by the addition of sodium hydroxide and hydrogen peroxide. This hydroboration changed the AMA units of the backbone to 3‐hydroxypropyl methacrylate, and an amphiphilic graft copolymer with a hydrophilic poly(3‐hydroxypropyl methacrylate) backbone and hydrophobic poly(St) side chains was obtained. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1195–1202, 2000  相似文献   

9.
Molecular motions of hydrophobic–hydrophilic water-soluble block copolymers in solution were investigated by high-resolution proton magnetic resonance (NMR). Samples studied include block copolymers of polystyrene–poly(ethylene oxide), polybutadiene–poly(ethylene oxide), and poly(ethylene oxide)–poly(propylene oxide)–poly(ethylene oxide). NMR measurements were carried out varying molecular weight, temperature, and solvent composition. For AB copolymers of polystyrene and poly(ethylene oxide), two peaks caused by the phenyl protons of low-molecular-weight (M?n = 3,300) copolymer were clearly resolved in D2O at 100°C, but the phenyl proton peaks of high-molecular-weight (M?n = 13,500 and 36,000) copolymers were too broad to observe in the same solvent, even at 100°C. It is concluded that polystyrene blocks are more mobile in low-molecular-weight copolymer in water than in high-molecular-weight copolymer in the same solvent because the molecular weight of the polystyrene block of the low-molecular-weight copolymer is itself small. In the mixed solvent D2O and deuterated tetrahydrofuran (THF-d8), two peaks caused by the phenyl protons of the high-molecular-weight (M?n = 36,000) copolymer were clearly resolved at 67°C. It is thought that the molecular motions of the polystyrene blocks are activated by the interaction between these blocks and THF in the mixed solvent.  相似文献   

10.
Vinyl chloride was polymerized at 59–92% of saturation pressure in a water-suspended system at 45–65°C with an emulsion poly(vinyl chloride) (PVC) latex as a seed. A water-soluble initiator was used in various concentrations. The monomer was continuously charged as vapor from a storage vessel kept at lower temperature. Characterization included determination of molecular-weight distribution and degree of long-chain branching by gel permeation chromatography (GPC) and viscometry, thermal dehydrochlorination, and microscopy. The polymerization rate decreases with decreasing pressure but is reasonable even at the lowest pressure. The molecular weight decreases with decreasing pressure and increasing initiator concentration and also with increasing polymerization temperature, if the initiator concentrations are chosen to give a constant initiator radical concentration. The degree of long-chain branching increases with increasing initiator concentration and decreasing monomer pressure but is unaffected by the polymerization temperature, if the initiator radical concentration is kept constant. The thermal stability decreases with decreasing M n, while the degree of long-chain branching has only a minor influence. The most important factor in the system influencing the molecular parameter is the monomer accessibility.  相似文献   

11.
The dehydrochlorination of different samples of PVC under vacuum with continuous removal of HCl by freezing, has been studied at 180–210°C. The comparison of the kinetic curves of the dehydrochlorination of various samples of PVC which were obtained by us and other investigators, with the theoretical curves for the thermal degradation of idealized PVC in the absence of HCl has been carried out. This had made it possible to evaluate the influence of unstable fragments present in the original polymer on the initial rate of PVC degradation quantitatively. It has been shown that the distinction between the stationary rates of the dehydrochlorination of various samples of PVC is determined by the difference of the values of the average length of dehydrochlorination chain, lav. The most probable interval of the values of lav has been ascertained to be 4–12. It is established that the most probable value of the constant of the rate of dehydrochlorination of normal links of PVC, k0, is 2.1 × 10?7?2.5 × 10?7 s?1 at 200°C. © 1993 John Wiley & Sons, Inc.  相似文献   

12.
Amphiphilic block and statistical copolymers of vinyl ethers (VEs) with pendant glucose residues were synthesized by the living cationic polymerization of isobutyl VE (IBVE) and a VE carrying 1,2:5,6‐di‐O‐isopropylidene‐D ‐glucose (IpGlcVE), followed by deprotection. The block copolymer was prepared by a two‐stage sequential block copolymerization, whereas the statistical copolymer was obtained by the copolymerization of a mixture of the two monomers. The monomer reactivity ratios estimated with the statistical copolymerization were r1 (IBVE) = 1.65 and r2 (IpGlcVE) = 1.15. The obtained statistical copolymers were nearly uniform with the comonomer composition along the main chain. Both the block and statistical copolymers had narrow molecular weight distributions (weight‐average molecular weight/number‐average molecular weight ∼ 1.1). Gel permeation chromatography, static light scattering, and spin–lattice relaxation time measurements in a selective solvent revealed that the block copolymer formed multimolecular micelles, possibly with a hydrophobic poly(IBVE) core and a glucose‐carrying poly(VE) shell, whereas the statistical copolymer with nearly the same molecular weight and segment composition was molecularly dispersed in solution. The surface properties of the solvent‐cast films of the block and statistical copolymer were also investigated with the contact‐angle measurement. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 459–467, 2001  相似文献   

13.
The single‐electron‐transfer/degenerative‐chain‐transfer mediated living radical polymerization (SET–DTLRP) of vinyl chloride (VC) in H2O/tetrahydrofuran at 25 °C catalyzed by thiourea dioxide [(NH2)2C?SO2] is reported. This polymerization occurs only in the presence of a basic sodium bicarbonate (NaHCO3) buffer and the electron‐transfer cocatalyst octyl viologen. The resulting poly(vinyl chloride) (PVC) has a number‐average molecular weight of 1500–7000 and a weight‐average molecular weight/number‐average molecular weight ratio of 1.5. This PVC does not contain detectable amounts of structural defects and has both active chloroiodomethyl and inactive chloromethyl chain ends. Because of possible side reactions caused by the primary sulfoxylate anion (SO), the catalytic activity of (NH2)2C?SO2 in the SET–DTLRP of VC is lower than that of the single‐electron‐transfer agent sodium dithionite. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 287–295, 2005  相似文献   

14.
The selectivity of the phenolysis reaction of a chlorine atom bound to a tertiary carbon ClT on a macromolecular model, i.e., the copolymer of vinyl chloride–isopropenyl chloride, was verified. The phenolysis reaction can be used as a chemical method to determine ClT in the copolymers. Phenolic polyelectrolytes are obtained as products. The increase of the ClT content leads to an appreciable decrease of the thermal stability of the polymer. The thermal decomposition by dehydrochlorination is a chain reaction. The γ and ultraviolet radiolysis processes did not reveal a remarkable influence of ClT; the samples with an increased ClT content showed a decreased stability towards sunlight. One concludes that when ClT is present in PVC it can initiate the decomposition reaction at lower temperatures than would be expected.  相似文献   

15.
Chain‐growth condensation polymerization of p‐aminobenzoic acid esters 1 bearing a tri(ethylene glycol) monomethyl ether side chain on the nitrogen atom was investigated by using lithium 1,1,1,3,3,3‐hexamethyldisilazide (LiHMDS) as a base. The methyl ester monomer 1a afforded polymer with low molecular weight and a broad molecular weight distribution, whereas the polymerization of the phenyl ester monomer 1b at ?20 °C yielded polymer with controlled molecular weight (Mn = 2800–13,400) and low polydispersity (Mw/Mn = 1.10–1.15). Block copolymerization of 1b and 4‐(octylamino)benzoic acid methyl ester ( 2 ) was further investigated. We found that block copolymer of poly 1b and poly 2 with defined molecular weight and low polydispersity was obtained when the polymerization of 1b was initiated with equimolar LiHMDS at ?20 °C and continued at ?50 °C, followed by addition of 2 and equimolar LiHMDS at ?10 °C. Spherical aggregates were formed when a solution of poly 1b in THF was dropped on a glass plate and dried at room temperature, although the block copolymer of poly 1b and poly 2 did not afford similar aggregates under the same conditions. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1357–1363, 2010  相似文献   

16.
A microphase‐separated, amphiphilic graft copolymer consisting of a poly (vinyl chloride) (PVC) backbone and poly(oxyethylene methacrylate) (POEM) side chains, (PVC‐g‐POEM at 62:38 wt %) was synthesized via atom transfer radical polymerization (ATRP). Nuclear magnetic resonance (1H NMR), FTIR spectroscopy, and transmission electron microscopy (TEM) clearly revealed that the “grafting from” method using ATRP was successful and that the graft copolymer molecularly self‐assembled into discrete nanophase domains of continuous PVC and isolated POEM regions. The self‐assembled graft copolymer film was used to template the growth of silver nanoparticles in solid state by introducing a AgCF3SO3 precursor and a UV irradiation process. The in situ formation of silver nanoparticles in the graft copolymer template film was confirmed by TEM, UV–visible spectroscopy, and wide angle X‐ray scattering. FTIR spectroscopy and X‐ray photoelectron spectroscopy also demonstrated the selective incorporation and in situ formation of silver nanoparticles within the hydrophilic POEM domains, presumably due to strong interactions between the silver and the ether oxygen in POEM. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3911–3918, 2008  相似文献   

17.
The single‐electron transfer living radical polymerization (SET‐LRP) of vinyl chloride (VC) initiated with CHBr3 in dimethylsulfoxide (DMSO) at 25 °C was investigated using Cu(0) powder and Cu(0) wire as the catalyst. It was determined that living kinetics and high conversion are achieved only through the proper calibration of the ratio between Cu(0) and TREN and the concentration of VC in DMSO. For both Cu(0) powder and Cu(0) wire, optimum conversion was achieved with higher levels of TREN than reported in earlier preliminary reports and under more dilute conditions. Using these conditions, 85+% conversion of VC could be achieved with Cu(0) powder and wire to produce white poly(vinyl chloride) (PVC) with Mn = 20,000 and Mw/Mn = 1.4–1.6 in 360 min. The use of Cu(0) wire provides the most effective catalytic system for the LRP of PVC allowing for simple removal and recycling of the catalyst. In the Cu(0) wire‐catalyzed SET‐LRP of VC, the consumption of Cu(0) was monitored as a function of conversion. From these studies, it is evident that the catalyst can be recycled extensively before significant exchange of Cu(0) into Cu(II)X2 and change in catalyst surface area is observed. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 164–172, 2010  相似文献   

18.
The cationic grafting of isobutylene, styrene, α-methylstyrene, and β-pinene from a poly(vinyl chloride) (PVC) backbone was investigated. Grafting-from was induced by Et2AlCl in 1,2-dichloroethane and methylene dichloride solutions from 20 to −70 °C. The effects of temperature and proton trap [2,6-di-tert-butylpyridine (DtBP)] on grafting-from efficiency (Geff), extent of grafting, branch length (molecular weight), and number of branches per PVC molecule were determined. Reducing the temperature invariably increased the Geff and the molecular weight of polyisobutylene, polystyrene, poly(α-methylstyrene), and poly(β-pinene) branches attached to PVC. The magnitude of the effects was different with the various olefins and depended on the reaction conditions. The effect of DtBP was examined in the 5 × 10−4–4 × 10−3 mol/L range. By increasing the DtBP concentration the Geff increased; however, the number-average molecular weight of the grafted branches decreased. The lengths of the grafted branches can be controlled, and Geff's close to 100% were obtained. The fact that the proton trap reduced the molecular weights of grafted branches suggests that besides proton scavenging, DtBP may also abstract protons from the growing carbenium ion site. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1675–1680, 2001  相似文献   

19.
α,ω‐di(iodo) poly(isobornyl acrylate) macroiniators (α,ω‐di(iodo)PIA) with number average molecular weight from M n,TriSEC = 11,456 to M n,TriSEC = 94,361 were synthesized by single electron transfer‐degenerative chain transfer mediated living radical polymerization (SET‐DTLRP) of isobornyl acrylate (IA) initiated with iodoform (CHI3) and catalyzed by sodium dithionite (Na2S2O4) in water at 35 °C. The plots of number average molecular weight vs conversion and ln{[M]0/[M]} vs time are linear, indicating a controlled polymerization. α,ω‐di(iodo) poly(isobornyl acrylate) have been used as a macroinitiator for the SET‐DTLRP of vinyl chloride (VCM) leading to high Tg block copolymers PVC‐b‐PIA‐b‐PVC. The dynamic mechanical thermal analysis of the block copolymers suggests just one phase indicating that copolymer behaves as a single material. This technology provides the possibility of synthesizing materials based on PVC with higher Tg in aqueous medium. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2009  相似文献   

20.
The polymerization of vinyl chloride (VC) with half‐titanocene /methylaluminoxane (MAO) catalysts is investigated. The polymerization of VC with the Cp*Ti(OCH3)3/MAO catalyst (Cp* = η5‐pentamethylcyclopentadienyl) afforded high‐molecular‐weight poly(vinyl chloride) (PVC) in good yields, although the polymerization proceeded at a slow rate. With the Cp*TiCl3/MAO catalyst, the polymer was also obtained, but the polymer yield was lower than that with the Cp*Ti(OCH3)3/MAO catalyst. The polymerization of VC with the Cp*Ti(OCH3)3/MAO catalyst was influenced by the MAO/Ti mole ratio and reaction temperature, and the optimum was observed at the MAO/Ti mole ratio of about 10. The optimum reaction temperature of VC with the Cp*Ti(OCH3)3/MAO catalyst was around 20 °C. The stereoregularity of PVC obtained with the Cp*Ti(OCH3)3/MAO catalyst was different from that obtained with azobisisobutyronitrile, but highly stereoregular PVC could not be synthesized. From the elemental analyses, the 1H and 13C NMR spectra of the polymers, and the analysis of the reduction product from PVC to polyethylene, the polymer obtained with Cp*Ti(OCH3)3/MAO catalyst consisted of only regular head‐to‐tail units without any anomalous structure, whereas the Cp*TiCl3/MAO catalyst gave the PVC‐bearing anomalous units. The polymerization of VC with the Cp*Ti(OCH3)3/MAO catalyst did not inhibit even in the presence of radical inhibitors such as 2,2,6,6,‐tetrametylpiperidine‐1‐oxyl, indicating that the polymerization of VC did not proceed via a radical mechanism. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 248–256, 2003  相似文献   

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