The radiation-induced postpolymerization of trioxane with 1,3-dioxolane has been investigated. Trioxane and 1,3-dioxolane were carefully purified in a rigorously dry, high-vacuum system. In the present study it was found that trioxane can be easily copolymerized with 1,3-dioxolane to give a copolymer having high molecular weight and excellent thermal stability. Typically, the isothermal weight loss after heating for 60 minutes under nitrogen at 222°C was 3.5% for a copolymer of trioxane and 1.0 wt-%1,3-dioxolane preirradiated with a dose of 1.0 × 105 Rad. The thermal stability of the copolymer was scarcely affected by the polymerization temperature and time, although it decreased slightly with increasing preirradiation dose. The dependences of the yield and inherent viscosity of the polymer on the preirradiation dosage, polymerization temperature and time were quite similar to those found for the homopolymerization of trioxane. The results were analyzed by using the kinetic scheme previously reported, and it was found that no chain transfer reaction occurs in this system. These results are discussed in comparison with those of homopolymerization reported previously. 相似文献
High molecular copolymers of trioxane with different cyclic ethers and formals were produced by γ-radiation from a 60Co source. It was polymerized in the solid state at 53°C. Polymerization does not occur in the melt. Irradiation was carried out with exclusion of air at a dose rate of 7 × 103 rad/hr. The polymerization rate was increased very considerably in the presence of 1,3-dioxolane and epichlorhydrin; the addition of other comonomers may reduce the yield. The concentration of the comonomer is generally higher in the polymer than in the initial mix. These comonomers which increase the polymerization rate are introduced preferentially into the polymer chain; this is proved by the unstable polymer part and the thermal stability. Experiments with the trioxane–1,3-dioxolane system revealed that the unstable polymer part is markedly reduced and the heat stability considerably inproved with rising concentrations of this monomer. The thermal stability and the reduced viscosity of these copolymers are within the range of technical processability. 相似文献
The γ-ray copolymerization of carbon monoxide with cyclic ethers, such as ethylene oxide, phenyl glycidyl ether, 1,3-dioxolane, 2-vinyl-1,3-dioxolane, terahydrofuran, 1,4-dioxane, and acetaldehyde was studied. A yellowish or brownish powdery copolymer was obtained in most of the cases examined. The infrared spectra showed that copolymers containing the ester structural unit were produced in the copolymerization with cyclic ethers which have no vinyl groups, and that a copolymer containing a ketone structure was produced from cyclic ether having vinyl group. It was found that the copolymer with ethylene oxide also had a β-propiolactone ring structure at the chain end or the side chain. The copolymers were confirmed to be partially crystalline from the x-ray diffraction diagrams. Further, a ring-opening polymerizability of the cyclic ether by γ-radiation was discussed. And it was found that as the bond dissociation energy between the carbon–oxygen linkage of the cyclic ether is small, the polymer yield both in the homopolymerization and copolymerization with carbon monoxide is high. A mechanism for the copolymerization is proposed on the basis of the results. 相似文献
Copolymerization of 1,3-dioxolane (DOX) with trioxane in the solid state was studied by radiation. The effects of radiation dose, DOX concentration, postpolymerization temperature and duration on the copolymer yield, and DOX incorporation were investigated and compared with published data. 相似文献
Homopolymerization and copolymerization of trioxane by use of various catalysts have been investigated. When MoO2(AcAc)2 is employed, crystalline homopolymers and copolymers as formed from polymerization exhibit significantly higher melting points than corresponding polymers prepared by use of ordinary cationic catalysts. The higher melting points are attributed to different morphology of the polymer chains formed during polymerization. We now call this phenomenon morphospecific polymerization. This communication describes our results in the copolymerization of trioxane and 1,3-dioxolane and some outstanding properties of the copolymers. A polymerization mechanism is also proposed. 相似文献
Trioxane–1,3-dioxolane copolymers of high molecular weights and good thermal stability are obtained with high yields by a crystallization-polymerization method. The feed consists of concentrated solutions of trioxane in cyclohexane in the presence of dissolved 1,3-dioxolane. The 1,3-dioxolane/trioxane molar ratio in the feed lies in the range 2 to 10%. The results are compared with those obtained from isothermal copolymerizations. 相似文献
Cationic copolymerization of 1,3,5-trioxane with methyl 10,11-epoxyundecanoate or methyl 7,8-epoxyoctanoate and terpolymerization with 1,3-dioxolane was successfully carried out. Co-and terpolymerization of 1,3,5-trioxane with 4-(1-carbomethoxynonyl)-1,3-dioxolane was also achieved. Feed compositions of the functional comonomers were varied from 5 to 40 mol %; in all cases the isolated copolymers contained less than 5% of the functional mer units. The composition of the copolymers showed that the methyl ω-epoxyalkanoates were much less reactive than 1,3,5-trioxane. A similar trend was observed with the functional dioxolane monomer, although significantly shorter induction periods were observed in comparison with the epoxy/trioxane copolymerizations. The oxymethylene copolymers and terpolymers were characterized primarily by their infrared spectra; however, the thermal and base stabilities of selected copolymers were also determined. 相似文献
The cationic ring-opening polymerization of trioxane and 1,3-dioxolane was found to be initiated by CO+CIO4? groups on a carbon black surface, which were introduced by the reaction of COCI groups with AgCIO4. The activation energy of the ring-opening polymerization of trioxane was estimated to be 15.5 kcal/mol. In the polymerization system, poly(oxymethylene) and poly(1,3-dioxolane) formed were effectively grafted onto carbon black depending upon the propagation of these polymers from the carbon black surface; for instance, the grafting ratio of poly(oxymethylene) onto carbon black increased with an increase in conversion and went up to about 180%. Although the grafted chain of poly(oxymethylene) was subject to stepwise thermal depolymerization from the chain ends, the thermal stability of poly(oxymethylene)-grafted carbon black was improved by acetylation of hemiformal end groups. The molecular weight of ungrafted poly(oxymethylene) formed in the polymerization was determined to be 1.8–2.0 × 104. Furthermore, the copolymerization of trioxane with 1,3-dioxolane, styrene, and other comonomers initiated by CO+CIO4? groups and the thermal stability of these acetal copolymer-grafted carbon black were investigated. 相似文献
1,3-Dioxolane was polymerized in the presence of ethylene glycol in order to prepare α,ω-dihydroxylated polymers which, upon reaction with pluriisocyanates yielded networks swellable in water. The crosslinks were made of urethane groups, which are bulky and hydrophobic. In order to expand the scope of the networks that can be envisioned, we have studied the replacement of the two end-standing hydroxylic groups by unsaturated polymerizable groups. Several methods are presented which allow successfully the quantitative endowment of the polymer endings with methacryloyl- or styryl- or vinylether-type groups. α,ω-dihydroxylated poly(1,3-dioxolane) was also metallated and used as a macroinitiator for the polymerization of ethylene oxide: the α,ω-dihydroxylated triblock copolymer obtained is made of a central poly(1,3-dioxolane) block flanked by two poly(ethylene oxide) ones. Several methods are also shown to be efficient in the characterization of the hydroxylic end-standing functions of the polymer. 相似文献
A kinetic study of the radiation-induced postpolymerization of trioxane in the solid state has been made. Trioxane was purified by sublimation through Ag2O and Na–K alloy in vacuo and was both irradiated and polymerized in a super-dry system under high vacuum. In the present study it was found that the initial rate of polymerization is larger than that reported previously. It is reasonably suggested that the postpolymerization of trioxane consists of two stages, i.e., a very large rate at the first stage and a relatively small one at the second stage. By using the kinetic scheme proposed previously kinetic parameters at the second stage were determined. It was found that trioxane can be postpolymerized even at a temperature below 30°C with good reproducibility and that the overall activation energy of the polymerization was less than 15 kcal/mole. No chain-transfer reaction seems to occur except at low temperatures. These results have been discussed in comparison with data reported previously. 相似文献
In order to investigate the effects of oxygen on the radiation-induced postpolymerization of trioxane in the solid state, a kinetic study has been made. Trioxane was purified by sublimation through Ag2O and Na-K alloy in vacuo and was irradiated and polymerized in the presence of rigorously dry oxygen. It was found that the initial rate of polymerization and the polymer yields are larger than those obtained in vacuo. By using the kinetic scheme proposed previously the results were analyzed kinetically. It was found that the influence of oxygen on the postpolymerization of trioxane is mainly attributable to the increase in the concentration of active species. The results obtained in dry air have been discussed in comparison with those in vacuo reported previously. 相似文献
Copolymerization of trioxane (TOX) and styrene oxide (STO) induced by gamma radiation was studied under varying operating conditions to see the effects of radiation dose, STO concentration, postpolymerization temperature, and duration on the polymer yield. Charging 5% STO with TOX STO conversion was 65% but yield was only 23% compared with 62% for the homopolymer. Molecular weight, melting point, density, and thermal stability of the copolymer samples were determined. 相似文献
In bulk polymerization and copolymerization of trioxane with ethylene oxide, it has been shown that p-chlorophenyldiazonium hexafluorophosphate is a superior catalyst as compared to boron trifluoride dibutyl etherate (BF3 · Bu2O). Polymers and copolymers of significantly higher molecular weight have been obtained. The higher molecular weight has been attributed primarily to less inherent chain transfer during propagation, which in turn can be attributed to the superior gegenion PF6?. The polymerization proceeds via a clear period followed by sudden solidification. Faster polymerization and higher molecular weight polymers have been observed for homopolymerization than for copolymerization. The polymer yield obtained after solidification is determined by both rate of polymerization and rate of crystallization of polymers. These rates, in turn, are dependent on the catalyst concentration. The molecular weight is determined both by polymer yield and extent of inherent chain transfer. In the range of monomer to catalyst mole ration [M]/[C] = (0.5–20) × 104 investigated, it has been found that in the higher range, the polymer yield is independent of the catalyst concentration and the extent of inherent chain transfer is inversely proportional to the half power of catalyst concentration: [M]/[C] = (0.5–8) × 104 for homopolymerization and (0.5–3) × 104 for copolymerization with 4.2 mole % ethylene oxide. In the lower range, the yield decreases with catalyst concentration and the extent of inherent chain transfer is inversely proportional to higher power of catalyst concentration. The dependence of molecular weight of polymers on catalyst concentration has been shown to be a complex one. The molecular weight goes through a maximum as the catalyst concentration is decreased. The maximum molecular weights have been obtained at [M]/[C] ≈ 8 × 104 for homopolymerization and ~3 × 104 for copolymerization with 4.2 mole % ethylene oxide. Prior to reaching maximum the molecular weight is inversely proportional to the half power of catalyst concentration indicating it is primarily controlled by inherent chain transfer. Upon further decrease of catalyst, molecular weight decreases as a result of both a decrease in polymer yield and an increase in inherent chain transfer. In copolymerization of trioxane and ethylene oxide, it has been ascertained that methylene chloride exhibits a favorable solvating effect. Although higher inherent chain transfer takes place in copolymerization than in homopolymerization, the extent of chain transfer is independent of ethylene oxide concentration. The difference in polymer yield and molecular weight a t different ethylene oxide concentrations is attributed primarily to the difference in kp/kt ratio. It also has been demonstrated that end capping of polymer chains can be accomplished by the use of a chain transfer agent—methylal. 相似文献
We, at Asahi Chemical in Japan, have industrialized three types of polyacetal resins, that is, the acetal homopolymer, copolymer and block copolymer using anionic, cationic and anionic polymerization techniques, respectively. During this industrialization, we observed various phenomena, which were not previously reported. First, the authors outline the three technologies for producing each type of polyoxymethylene from an industrial viewpoint. Next, the authors discuss a newly found reaction during the induction period of the trioxane and ethylene oxide copolymerization. Experimental proof of direct ring expansion between the reaction of trioxane and ethylene oxide is discussed and various novel cyclic compounds are also shown. To the best of our knowledge, this reaction may be the world's first experimental proof of direct ring expansion of the reaction of a cyclic monomer. Third, the authors also discuss the newly founded morphospecific polymer from the copolymerization of trioxane and ethylene oxide using boron trifluoride dibutyl ether as an initiator. 相似文献
In order to assess the effect of the methylol group at the 4-position of 1,3-dioxolane on polymerization, the photopolymerization of 2-vinyl-4-hydroxymethyl-1,3-dioxolane (VHDO) was carried out in benzene at 40°C. The reaction scheme of VHDO was considered to be the same as that of 2-vinyl-1,3-dioxolane (VDO). The rate of polymerization and the molecular weight of polymer were small because of the degradative chain transfer by allylidene group. Moreover, the rate of polymerization of VHDO was greater than that of VDO, whereas the molecular weight of polymer of VHDO was less than that of VDO. 相似文献
The radiation-induced solid-state polymerization of 3,3-bischloromethyloxetane (BCMO) was investigated by direct observation of the development of the morphology of the growing polymer phase in single crystals of the monomer. Electron microscopy shows that the polymerization gives rise to amorphous polymer in the first step. The polymer forms irregular platelets which aggregate into larger units without reflecting the crystalline order of the monomer. Subsequent to polymerization, the amorphous polymer crystallizes to the β-modification of poly-BCMO. If the partially polymerized crystals are extracted by solvents of the monomer, crystallization of the polymer is enhanced, and morphological artifacts arise which were previously mistaken for the true morphology of the “as polymerized” polymer. The copolymerization behavior of solid solutions of 3-ethyl-3-chloromethyloxetane (ECMO) and BCMO does not differ from the liquid bulk copolymerization with respect to copolymer composition, which is different from the composition of the monomer mixture. It is concluded that the polymer chains grow in noncrystalline zones as in a polymerization in the liquid state by which amorphous polymer is formed. No lattice control was observable in this solid-state polymerization. 相似文献