Photoinduced ionic polymerization. VII. Cationic polymerization of cyclohexene oxide in solid state

Photopolymerization of cyclohexene oxide in the presence of electron acceptors was studied in a bulk system (in liquid as well as in solid states). The polymerization was proved to proceed by a cationic mechanism in both states by the effect of inhibitors. In a liquid phase the light intensity dependence of the rate of polymerization and the molecular weight distribution showed a contribution of a free ionic polymerization. Any discontinuous phenomenon in the rate as well as in the molecular weight was not discerned between liquid(above ?36°C) and plastic crystal (between ?36 and ?81°C) phases. A quantum yield of monomer consumption as high as 8 × 10³ was observed in the plastic crystal phase. Below ?81°C in the normal crystal phase the rate as well as the molecular weight was remarkably suppressed.     

Ring‐opening polymerization of the cyclic dimer of poly(trimethylene terephthalate)

Poly(trimethylene terephthalate) (PTT) was prepared by the ring‐opening polymerization of its cyclic dimer. Antimony(III) oxide, titanium(IV) butoxide, dibutyltin oxide, and titanium(IV) isopropoxide were used as catalysts. Among the catalysts, titanium(IV) butoxide was the most effective for the same reaction conditions. A weight‐average molecular weight of 63,500 g/mol was obtained from ring‐opening poly merization at 265 °C for 2 h in the presence of 0.5 mol % titanium(IV) butoxide. The PTTs obtained from the polymerization catalyzed with increasing amounts of antimony(III) oxide showed increasing weight‐average molecular weights and reaction conversions. When 1 mol % antimony(III) oxide was used, the weight‐average molecular weight was 32,000 g/mol and the conversion was 82% after 1 h of polymerization at 265 °C. In the case of the polymer catalyzed by titanium(IV) butoxide under the same conditions, the weight‐average molecular weight and conversion were 40,000 g/mol and 77% when 0.25 mol % was used, whereas 0.5 mol % catalyst produced a weight‐average molecular weight of 27,000 g/mol and a conversion of 95%. To get an acceptable molecular weight and relatively high reaction conversion, a catalyst concentration of at least 0.5 mol % was found to be necessary, in contrast to conventional condensation polymerizations, which require only about one‐tenth of this amount of the catalyst. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6801–6809, 2006     

Nitroxide-mediated photo-living radical polymerization of vinyl acetate

The photoradical polymerization of vinyl acetate was performed using 4-methoxy-2,2,6,6-tetramethylpiperidine-1-oxyl (MTEMPO) as the mediator in the presence of bis(alkylphenyl)iodonium hexafluorophosphate (BAI). The MTEMPO/BAI system using 2,2’-azobis(isobutyronitrile) or 2,2’-azobis(4-methoxy-2,4-dimethylvaleronitrile) as the initiator did not succeed in controlling the molecular weight and produced polymers that showed a bimodal gel permeation chromatography with the broad molecular weight distribution. On the other hand, the polymerization using 1-(cyano-1-methylethoxy)-4-methoxy-2,2,6,6-tetramethylpiperidine and BAI proceeded by the living mechanism based on linear increases in the first order time–conversion and conversion–molecular weight plots. The molecular weight distribution also increased with the increasing conversion due to cloudiness of the solution as the polymerization proceeded. It was found that the polymerization had a photolatency because the propagation stopped by interruption of the irradiation and was restarted by further irradiation.     

Synthesis of zwitterionic block copolymers via RAFT polymerization

A series of poly [2-(dimethylamino)ethyl methacrylate (DMA)-sodium acrylate (SA)] diblock copolymers were synthesized using reversible addition-fragmentation chain transfer (RAFT) polymerization. The polymerization exhibits controlled characters: well-controlled molecular weight, narrow molecular weight distribution, molecular weight increasing with polymerization time. The zwitterionic diblock copolymers show rich solution behaviors. Dynamic light scattering (DLS) indicated the formation of micelles and reverse micelles of copolymers is affected by net charge density of copolymers. Microcalorimetry studies showed that the lower critical solution temperature (LCST) increases with incorporation of hydrophilic segments in buffer.     

提高聚环氧丙烷分子量的研究

本文采用丙二醇—钾、丙二醇引发环氧丙烷（PO）的阴离子聚合，同时加入络合剂，发现聚合反应速度加快，同时能有效提高聚环氧丙烷（PPO）的分子量。通过探索合成工艺条件，得到了■为4，000的线型聚环氧丙烷。     

Ferric oxide-catalyzed polymerization of methyl methacrylate

The polymerization of methyl methacrylate was carried out in water at various concentrations of sodium bisulfite, ferric oxide, and methyl methacrylate at 30, 40, and 50°C. The effect of ferric oxide on the rate of polymerization was studied at 50°C. Rates of polymerization increased in the presence of ferric oxide. For example, the rate of polymerization increased from 3.4 × 10^?5 mole/l.-sec to 11.8 × 10^?5 mole/l.-sec when the ferric oxide concentration was varied from 0 to 15 g/l. water. The molecular weight of the polymer decreased from an average of 1.4 × 10⁶ in the absence of ferric oxide to 2.8 × 10⁵ when the ferric oxide was present. The variation of molecular weight of the polymers with temperature and conversion was studied. At a fixed conversion of 80%, the average molecular weight decreased from 3.4 × 10⁵ at 30°C to 2.2 × 10⁵ at 50°C. The average molecular weight was also found to increase with increasing monomer and initiator concentrations. It increased from 8.1 × 10⁴ to 5.3 × 10⁵ and from 3.4 × 10⁵ to 8.9 × 10⁵ as the initiator and monomer concentrations increased from 0.01 to 0.05 mole/l. and from 0.235 to 0.705 mole/l., respectively. The apparent energy of activation for the polymerization was found to be 15.6 and 9.7 kcal/mole in absence and in presence of ferric oxide, respectively.     

Photoinitiated polymerization of methacrylates comprising phenyl moieties

Investigation of photopolymerization kinetics of 4-(4-methacryloyloxyphenyl)-butan-2-one (1) in comparison with 2-phenoxyethyl methacrylate (2) and phenyl methacrylate (3) using a UV-LED emitting at 395 nm shows significantly faster polymerization of 1 compared to both 2 and 3 at 40°C. Vitrification affects photopolymerization kinetics of all methacrylates under investigation. Interestingly, quantitative final conversion is observed during photoinitiated polymerization of 1 and 2 whereas 3 shows limited conversion at about 80%. Furthermore, higher degree of polymerization is obtained by photoinitiated polymerization of 1 compared to 2 and 3. This shows that the 3-oxobutyl substituent at the phenyl ring of 1 significantly affects both polymerization kinetics and final conversion of the photoinitiated polymerization. Moreover, an additional higher molecular weight fraction is observed in case of polymerization of 1 at 85°C that is above the glass transition temperature of the polymer formed during photoinitiated polymerization. As a thermal polymerization at 85°C in the absence of light results in a high molecular weight polymer as well, an additional thermal process may be discussed as reason for the higher molecular weight polymer fraction in case of the photopolymer made at 85°C.     

Tertiary amine-functionalized polymers by atom transfer radical polymerization

The quantitative synthesis of tertiary amine-functionalized polymers by atom transfer radical polymerization is reported. Tertiary amine-functionalized polystyrene was prepared with the adduct of 1-(bromoethyl)benzene with 1-(4-dimethyl-aminophenyl)-1-phenylethylene as an initiator in the atom transfer radical polymerization of styrene in the presence of a copper (I) bromide/2,2′-bipyridyl catalyst system. The polymerization proceeded via a controlled free-radical polymerization process to afford quantitative yields of the corresponding tertiary amine-functionalized polystyrene with predictable number-average molecular weights (1600–4400), narrow molecular weight distributions (1.09–1.31), and an initiator efficiency of 0.95. The polymerization process was monitored by gas chromatographic analysis. The tertiary amine-functionalized polymers were characterized by thin-layer chromatography, size exclusion chromatography, potentiometry, and spectroscopy. All experimental evidence was consistent with quantitative functionalization via the 1,1-diphenylethylene derivative. Polymerization kinetic measurements showed that the polymerization reaction followed first-order-rate kinetics with respect to monomer consumption and that the number-average molecular weight increased linearly with monomer conversion. © 2001 John Wiley & Sons, Inc. J Polym Sci A Part A: Polym Chem 39: 2058–2067, 2001     

Titanium alkoxides as initiators for the controlled polymerization of lactide

Fourteen titanium alkoxides were synthesized for comparison of their catalytic properties in the bulk and solution polymerization of lactide (LA). In bulk polymerizations, they are effective catalysts in terms of polymer yield and molecular weight. Titanatranes gave polylactides with significantly increased molecular weight over more extended polymerization times, and those with five-membered rings afforded polymers in higher yields and with larger molecular weights than their six-membered ring counterparts. Steric hindrance of the rings was found to significantly affect polymer yields. Increased heterotactic-biased poly(rac-LA) was formed as the number of chlorine atoms increased in TiCl(x)(O-i-Pr)(4)(-)(x). In solution polymerizations, titanium alkoxides catalyzed controlled polymerizations of LA, and end group analysis demonstrated that an alkoxide substituent on the titanium atom acted as the initiator. That polymerization is controlled under our conditions was shown by the linearity of molecular weight versus conversion. A tendency toward formation of heterotactic-biased poly(rac-LA) was observed in the solution polymerizations. The rate of ring-opening polymerization (ROP) and the molecular weight of the polymers are greatly influenced by the substituents on the catalyst, as well as by factors such as the polymerization temperature, polymerization time, and concentration of monomer and catalyst.     

Photo-living radical polymerization of methyl methacrylate using alkoxyamine as an initiator

The photoradical polymerization of vinyl acetate was performed using 4-methoxy-2,2,6,6-tetramethylpiperidine-1-oxyl (MTEMPO) as the mediator in the presence of bis(alkylphenyl)iodonium hexafluorophosphate (BAI). The MTEMPO/BAI system using 2,2’-azobis(isobutyronitrile) or 2,2’-azobis(4-methoxy-2,4-dimethylvaleronitrile) as the initiator did not succeed in controlling the molecular weight and produced polymers that showed a bimodal gel permeation chromatography with the broad molecular weight distribution. On the other hand, the polymerization using 1-(cyano-1-methylethoxy)-4-methoxy-2,2,6,6-tetramethylpiperidine and BAI proceeded by the living mechanism based on linear increases in the first order time–conversion and conversion–molecular weight plots. The molecular weight distribution also increased with the increasing conversion due to cloudiness of the solution as the polymerization proceeded. It was found that the polymerization had a photolatency because the propagation stopped by interruption of the irradiation and was restarted by further irradiation.     

Use of block copolymer surfactants in the inverse-suspension polymerization of acrylamide

A comprehensive experimental investigation of the inverse microsuspension polymerization of acrylamide using an oil-soluble initiator and a block copolymeric surfactant whose hydrophobic miety is poly(12-hydroxystearic acid) and whose hydrophilic moeity is polyethylene oxide was carried out. It was found that the initial polymerization rate was first order with respect to molar monomer concentration, first order with respect to molar initiator concentration and zeroth order with respect to molar emulsifier concentration. Based on these experimental findings, a mechanism was proposed which includes initiation, propagation transfer to monomer and termination. It also includes transfer to impurities which are believed to be found in the surfactant. The kinetic model developed from the proposed mechanism is found to be in good agreement with the experimental conversion and weight-average molecular weight data. Comparing with sorbitan esters of fatty acids, the copolymeric surfactant provides higher polymerization rate and very high and linear molecular weight comparable to those obtained by solution polymerization.     

Selective polymerization of propylene oxide by a tin phosphate coordination polymer

Oligomeric and polymeric polyether polyols, especially poly(propylene oxide), are used for the production of detergents, nonionic surfactants, washing agents, and cleaners, but they are predominantly used in polyurethane production processes. Tin phosphate coordination polymers show good activity in the selective polymerization of epoxides. The catalyst can be easily synthesized by the condensation of tributyl phosphate and butyl tin trichloride. Investigations of this achiral organotin phosphate condensate in the stereoregular polymerization of propylene oxide, including the properties controlling the molecular weight of the resulting poly(propylene oxide) and structural and mechanistic studies, are presented. Additionally, the polymerization of propylene oxide occurs with high activity, no allyl end groups, just a small number of irregularities, and a high percentage of isotacticity (88%) in the polymer. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3032–3041, 2007     

Molecular weight distribution of poly-N-vinylcarbazole obtained in catalytic solid-state polymerization

The molecular weight distribution of poly-N-vinylcarbazole (PVCar) obtained in solid-state polymerization with various catalysts or γ-rays was measured by gel-permeation chromatography, in order to determine the mechanism of the solid-state polymerization. In addition, the molecular weight distribution of PVCar obtained in the solution polymerization by the cationic catalyst was also measured. The molecular weight distribution of PVCar obtained in the catalytic solid-state polymerization was broad and had three peaks, independent of the nature of catalysts, radical and cationic. A large amount of low molecular weight oligomer (probably dimer or trimer) was formed in the catalytic solid-state polymerization of VCar. The molecular weight distribution of PVCar obtained in the cationic solution polymerization showed only one sharp peak. On the other hand, the molecular weight of PVCar obtained in the radiation-induced solid-state polymerization was larger than that obtained in the catalytic solid-state polymerization, and dimer or trimer was not formed. The molecular weight distribution of PVCar obtained was composed of one sharp peak in the high molecular weight region, and a broad peak in the low molecular weight region, and was extremely different from that of PVCar obtained in the catalytic solid-state polymerization.     

Photoinduced ionic polymerization. V. Coexistence of cationic and anionic polymerizations

Photopolymerization of a mixture of cyclohexene oxide and nitroethylene was carried out with the purpose of carrying out cationic and anionic polymerizations simultaneously in the same system. The excitation of the charge transfer band by light of wavelength longer than 390 nm gives rise to the polymerization of both monomers. No polymer was obtained in the dark. Additives affect the composition of the polymer, the rates of polymerization, and the molecular weight distributions. These data show that cationic polymerization of cyclohexene oxide and anionic polymerization of nitroethylene occurs simultaneously in this system.     

Solvent‐free ring‐opening polymerization of cyclohexene oxide catalyzed by palladium chloride

In this study, we have for the first time demonstrated that palladium chloride (PdCl₂) is an efficient catalyst for ring‐opening polymerization of cyclohexene oxide in a solvent‐free condition. The polymerization product was in atactic structure, and reaction conditions, such as reaction temperature, time, and catalyst amount, showed effects on polymerization conversion yield, turnover number, and number‐average molecular weight of the resulting poly(cyclohexene oxide). PdCl₂ catalysis follows a cationic ring‐opening mechanism. The polymerization result is highly determined by the chemical structure of the monomers.     

Radical polymerization of ethyl acrylate with dead end polymerization conditions

The radical polymerization of ethyl acrylate (EA) with 4,4^′-azobis(4-cyanovaleric)acid as initiator was investigated in propionitrile at 363 K in order to obtain carboxy-telechelic oligo(ethyl acrylate). The results of functionality and molecular weights showed that a transfer reaction had occurred. A molecular weight study was performed in order to show the importance of transfer to solvent due to the high reactivity of the EA radical. Finally, the radical polymerization was investigated at very low temperature (253-273 K), using a redox system initiation. A behavior of dead end polymerization was observed but the activation energy of propagation for EA is still high and does not allow the synthesis of a telechelic oligomer.     

Ring-opening polymerization of α,β-disubstituted oxiranes by α-methoxyphenylmethylium hexachloroantimonate

α-Methoxyphenylmethylium hexachloroantimonate was used as a novel initiator for the polymerization of α,β-disubstituted oxiranes such as cyclohexene oxide (CHO) and 2-butene oxide (trans and cis) (2-BO) at ?78°C with dichloromethane or dichloromethane-toluene mixtures as solvents. The CHO polymerization mixture became turbid and the polymer precipitated in dichloromethane. The CHO polymerization proceed quantitatively in dichloromethane–toluene mixtures. The molecular weight distribution of polyCHO obtained was bimodal regardless of the solvent used. The polymerization of trans-2-BO was heterogeneous in both dichloromethane and dichloromethane–toluene mixture. The polymerization mixtures of cis-2-BO were transparent but reached a limit yield which was less than the polymer yield of trans-2-BO. Furthermore, the microstructure of the poly2-BOs were analyzed by Vandenberg's method and the results confirmed Vandenberg's finding that inversion of configuration occurs in the propagation step.     

LCP aromatic polyesters by esterolysis melt polymerization

Polyarylates have previously been synthesized from acetate esters via esterolysis (loss of methyl acetate). This polycondensation can be extended to p‐substituted aromatic monomers for liquid crystal polyesters (LCPs). For AB‐type polymers, methyl p‐acetoxybenzoate and methyl 6‐acetoxynaphthoate were copolymerized to an LCP with reasonable molecular weights. Benzoate esters, methyl 4‐benzoyloxybenzoate (MBB) and methyl 6‐benzoyloxy‐2‐naphthoate (MBN), are also investigated. Several tin and antimony oxide catalysts were effective. The rate of esterolysis polymerization of MBB and MBN is slower than that of the corresponding acidolysis melt polymerization, but fast enough to give relatively high‐molecular‐weight polymers and similar thermal stability as commercial LCP prepared by acidolysis. Using these alternative benzoyloxy groups significantly reduced the color problem, because ketene loss cannot occur. Esterolysis melt polymerizations leading to AB/AABB‐type LCPs were performed using either dimethyl 2,6‐naphthalene dicarboxylate (DMND) or dimethyl terephthalate (DMT) with methyl 4‐acetoxybenzoate and phenylhydroquinone diacetate with tin and antimony catalysts. DMT‐based monomer compositions show much faster polymerization than DMND‐based compositions using antimony oxide catalyst. All these LCPs show a T_g in the 140–170 °C range as a result of the inclusion of the naphthalene and/or phenyl hydroquinone units in the polymer chain. Compositions completely off‐balanced on either side still lead to relatively high‐molecular‐weight copolyesters because either excess monomer can be removed during polymerization. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3586–3595, 2000     

Preparation of polyvinylpyrrodione microspheres by dispersion polymerization

The preparation of polyvinylpyrrolidone (PVP) microspheres in ethyl acetate by dispersion polymerization with N-vinylpyrrolidone (NVP) as initial monomer, poly(N-vinylpyrrolidone-co-vinyl acetate) (P (NVP-co-VAc)) as dispersant, and 2, 2′-azobisisobutyronitrile(AIBN) as initiator is reported. The influences of monomer concentration, dispersant concentration and initiator concentration on the size of PVP microspheres as well as the monomer conversion were studied. The structure and properties of PVP microspheres were analyzed. The results show that the prepared PVP microspheres have a mean diameter of 3-4 μm. With an increase in NVP concentration, the size and the molecular weight of the PVP microspheres as well as the monomer conversion all increase. With increasing P(NVP-co-VAc) concentrations, the PVP molecular weight and monomer conversion both increase while the size of the microspheres becomes smaller. As the concentration of AIBN increases, the microsphere size and monomer conversion increase whereas the PVP molecular weight decreases. The PVP prepared by dispersion polymerization has a crystal structure, and its molecular weight is lower compared to that prepared by solution polymerization. __________ Translated from Acta Polymerica Sinica, 2007, 11 (in Chinese)     

Temperature- and pH-responsive star amphiphilic block copolymer prepared by a combining strategy of ring-opening polymerization and reversible addition-fragmentation transfer polymerization

The star-shaped poly(ε-caprolactone)-b-poly(2-(dimethylamino)ethyl methacrylate) (HPs-Star-PCL-b-PDMAEMA) was synthesized by ring-opening polymerization and reversible addition-fragmentation chain transfer (RAFT) polymerization. Star-shaped polycaprolactones (HPs-Star-PCL) were synthesized by the bulk polymerization of ε-caprolactone (CL) with a hyperbranched polyester initiator and tin 2-ethylhexanoate as a catalyst. The number-average molecular weight of these polymers linearly increased with the increase of the molar ratio of CL to hyperbranched initiator. HPs-Star-PCL was converted into a HPs-star-PCL-RAFT by an esterification of HPs-Star-PCL and 4-cyanopentanoic acid dithiobenzoate. Star amphiphilic block copolymer HPs-Star-PCL-b-PDMAEMA was obtained via RAFT polymerization of 2-(dimethylamino)ethyl methacrylate (DMAEMA). The molecular weight distribution of HPs-Star-PCL-b-PDMAEMA was narrow. Furthermore, the micellar properties of HPs-Star-PCL-b-PDMAEMA in water were studied at various temperatures and pH values by means of dynamic light scattering (DLS). The results indicated that the star copolymers had the pH- and temperature-responsive properties. The release behaviors of model drug aspirin from the star polymer indicated that the rate of drug release could be effectively controlled by pH value and temperature.