Specific phenomena during the copolymerization of trioxane and ethylene oxide

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.     

Novel reaction between cyclic formal and ethylene oxide

Novel reactions between trioxane and ethylene oxide were discovered, and three novel cyclic formals were isolated and identified. These novel cyclic compounds clarified the initiation mechanism of the copolymerization of trioxane and ethylene oxide. This type of reaction was not limited to the reaction between trioxane and ethylene oxide but was also generalized to the reaction between the cyclic formal and ethylene oxide. Although an NMR method for analyzing the ethylene oxide sequences of the acetal copolymer from trioxane and ethylene oxide has not yet been established, the three newly found novel cyclic compounds, composed of 1 mol of ethylene oxide and 1 mol of trioxane, 2 mol of ethylene oxide and 1 mol of trioxane, and 3 mol of ethylene oxide and 1 mol of trioxane, were useful for analyzing the ethylene oxide sequences. These compounds gave only one consecutive oxyethylene unit, two consecutive oxyethylene units, and three consecutive oxyethylene units in three consecutive oxymethylene units, respectively, and gave different ¹H NMR spectra for each oxyethylene unit. Considering these data, we synthesized three polymeric model compounds that had one consecutive oxyethylene sequence, two consecutive oxyethylene sequences, and three consecutive oxyethylene sequences in an oxymethylene main chain. By a linear combination of the ¹H NMR spectrum of each oxyethylene unit of the three polymeric model compounds, we succeeded in determining the ethylene oxide sequences by the ¹H NMR method for the copolymer from trioxane and ethylene oxide. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 520–533, 2004     

Chain end analysis of bisphenol A polysulfone and its relation to molecular weight

The preparation of amine-terminated polysulfone by step polymerization of the monomers bisphenol A and dichlorodiphenyl sulfone in the presence of end-capping reagent 4-aminophenol was investigated. A persistent problem with end-capping strategy as applied to step polymerization is the presence of end groups other than those introduced by the end-capping reagent. These unintended end groups, which can persist in the polymer product even when 100% of the end-capping reagent has reacted, are associated with a proportionate decrease in polymer chain length. This situation renders quantitative analysis of a single type of end group invalid as a method for molecular weight determination. The presence of unintended end groups does not appear to correlate with a particular set of reaction conditions; unintended end groups were found to occur in polymerizations conducted under strong base conditions (NaOH), under weak base conditions (K₂CO₃), and with a wide range of monomer feed ratios. A scheme for unambiguous quantification of chain ends and molecular weight for end-capped polysulfone is described. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1309–1316, 1998     

Selective degradation of silicone copolymers and networks

An exhaustive end-capping method for the analysis of silicone copolymers and networks using hexamethyldisiloxane in the presence of trifluoromethanesulfonic acid was demonstrated. The hard block of a polymide-co-polysiloxane was isolated by the equilibration of the copolymer with a large excess of hexamethyldisiloxane and subsequently examined by size exclusion chromatography. Addition cured polyimidesiloxane networks were also equilibrated with an excess of the disiloxane and the resulting oligmoers characterized by gas chromatography of the end-capped fragments.     

Synthesis and Characterization of Novel Hydrophobically End-Capped Poly(ethylene oxide)s [PEOs]

We report on the synthesis and characterization of a novel hydrophobically modified end-capped poly(ethylene oxide)s. The end-capping agent of this polymer was designed and synthesised from a renewable resource material namely, gallic acid (i.e. 3,4,5-trihydroxybenzoic acid), the byproduct of tannin industry. The hydroxyl groups at 3, 4 and 5 positions of gallic acid provide an opportunity for varying the hydrophobicity of the compound. The hydrophobic end-capping compound, 3,4,5-tridodecyloxy bezoylazide was prepared from gallic acid and PEGs with different chain lengths (of number average molecular weights, 10000 and 35000 g/mol) were end-capped using 3,4,5-tridodecyloxybenzoyl azide. The quantitative analysis of end-capping in the polymers was demonstrated by ¹H-NMR spectroscopy and the rheological studies were carried out in the surfactant solutions.     

Radiation-induced postpolymerization of trioxane in the solid state. V. Studies on copolymer composition

Studies on the composition of copolymers obtained by the radiation-induced solid-state postpolymerization of trioxane with 1,3-dioxolane have been carried out. Gas-chromatographic analysis of the reaction mixtures showed that most of the 1,3-dioxolane disappears rapidly from the reaction system in an early stage of polymerization, and that the fraction of ethylene oxide units in the copolymer chain [E] decreases markedly with increasing polymer yield. This finding was confirmed by NMR spectra of the copolymer. DSC thermograms of the copolymer indicated that the relationship between the melting point and the average composition of copolymers prepared in this study differed from that found for copolymers in which comonomer units are distributed statistically in the polymer chain. It was suggested that the copolymer formed by the radiation-induced solid-state postpolymerization of trioxane–1,3-dioxolane is characterized by a heterogeneous distribution of ethylene oxide units in the copolymer chain. It was also found that, in the radiation-induced solid-state postpolymerization of trioxane–1,3-dioxolane, the amount of tetraoxane formation increased linearly with increasing polymer yield. Although it is extremely small compared with that obtained in solution polymerization, it is slightly larger in the trioxane–1,3-dioxolane system than in the trioxane system.     

Analysis of ethylene oxide sequences of the acetal copolymer from trioxane and ethylene oxide

An NMR method for the analysis of the ethylene oxide sequence of the acetal copolymer from trioxane and ethylene oxide has not yet been established. We found three novel cyclic compounds composed of 1 mol of ethyelene oxide and 1 mol of trioxane, 2 mol of ethylene oxide and 1 mol of trioxane, and 3 mol of ethylene oxide and 1 mol of trioxane. These compounds gave only one consecutive oxyethylene unit, two consecutive oxyethylene units, and three consecutive oxyethylene units in three consecutive oxymethylene units, respectively, and gave different ¹H NMR spectra for each oxyethylene unit. Considering these data, we synthesized three polymeric model compounds that have one consecutive oxyethylene sequence, two consecutive oxyethylene sequences, and three consecutive oxyethylene sequences in an oxymethylene main chain. By a linear combination of the ¹H NMR spectrum of each oxyethylene unit of the three polymeric model compounds, we succeeded in determining the ethylene oxide sequence by the ¹H NMR method for the copolymer from trioxane and ethylene oxide. Good agreement was observed between the ¹H NMR method and the hydrolysis method for the analysis of the ethylene oxide sequences. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3239–3245, 2001     

Electroinitiated polymerization of trioxane in chlorinated hydrocarbons

The electroinitiated polymerization of trioxane in chlorinated hydrocarbons, with tetrabutyl-ammonium perchlorate as background electrolyte, has been investigated. The initiation always involves perchlorate oxidation but the polymerization exhibits different features in the various solvents. It has been found that in 1–2 dichloroethane the polymerization, once started by a short pulse of current, proceeds without any induction period to moderate conversion of monomer to polymer. The initial rate of polymerization depends linearly on the monomer cone, and on the initiating charge, so allowing determination of some kinetic parameters. On the other hand, the electroinitiated polymerization of trioxane in dichloromethane requires continuous current to give reasonable conversions; it exhibits induction periods and acceleration which cannot be simply related to the current.     

Molar Mass Dispersity Control by Iodine-mediated Reversible-deactivation Radical Polymerization

Dispersity(D)of polymers has a great effect on the properties of polymeric materials,and therefore how to control D is very important but still a huge challenge in polymer synthesis,especially for reversible-deactivation radical polymerization(RDRP)strategy.Herein,we successfully developed a novel strategy to adjust D of polymers by visible light-controlled reversible complexation mediated living radical polymerization(RCMP)and combination of single-electron transfer-degenerative chain transfer living radical polymerization(SET-DTLRP)at room temperature.In RCMP system,2-iodo-2-methylpropionitrile(CP-I)and ethyl 2-iodo-2-phenylacetate(EIPA)were used as alkyl iodide initiators,by using methyl methacrylate(MMA)as the model monomer and n-butylacrylate(BA)as the end-capping reagent to regulate D of polymers.Subsequently,we successfully prepared the block copolymer PMMA-b-PBA with adjustable D by reactivating the polymer end-chains via SET-DTLRP in the presence of copper wire,fully demonstrating that it is a promising strategy that can keep the"living"feature of polymers while regulating their molar mass dispersities easily.     

Block copolymerization. VII. Kinetic studies on the polymerization of pivalolactone with polystyrene dicarboxylates and polyacrylonitrile dicarboxylates

The rate of anionic polymerization of pivalolactone with polystyrene dicarboxylates decreased with conversion, suggesting deactivation of the propagating chain end by precipitation of the polymer during polymerization. The presence of unreacted initiator was explained by slow initiation for formation of a living polymer of pivalolactone. Various factors affecting block efficiency were discussed, and high efficiency was obtained for the preparation of block copolymers containing a long pivalolactone segment by using more nucleophilic polystyrene dicarboxylates. Block copolymer of acrylonitrile and pivalolactone was prepared from polyacrylonitrile dicarboxylates.     

Radiation-induced postpolymerization of trioxane in the solid state. IV. Copolymerization of trioxane with dioxolane

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.     

Synthesis of anionic amphiphilic carbosilane block copolymer: Poly(1,1‐diethylsilacyclobutane‐block‐methacrylic acid)

An amphiphilic block copolymer of silacyclobutane and methacrylic acid (MAA) was synthesized via a living anionic polymerization of 1,1‐diethylsilacylcobutane (EtSB). Sequential addition of 1,1‐diphenylethylene and t‐butyl methacrylate (tBMA) to living poly(EtSB) in the presence of lithium chloride gave poly(EtSB‐block‐tBMA) with narrow molecular weight distributions. The t‐butyl ester groups in the obtained polymer were readily hydrolyzed via heating in 1,4‐dioxane in the presence of concentrated aqueous hydrochloric acid. The block copolymer with a short MAA segment was soluble in chloroform and insoluble in methanol and basic water, whereas the block copolymer with a long MAA segment was soluble in methanol and basic water and insoluble in chloroform. The block polymer (EtSB/tBMA = 45/60) formed a monolayer film on the water surface; this was confirmed by surface pressure measurement. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 86–92, 2001     

Initiator‐fragment incorporation radical polymerization of divinylbenzene in the presence of glyoxylic oxime ether: Formation of soluble hyperbranched polymer

The copolymerization of divinylbenzene (DVB) and ethylstyrene (EtSt) was carried out at 70 and 80 °C in benzene with dimethyl 2,2‐azobisisobutyrate (MAIB) at high concentrations as initiator in the presence of methyl benzyloxyiminoacetate (MBOIA), a glyoxylic oxime ether, as a retarder. The copolymerization system of DVB (0.25 mol/L), EtSt (0.25 mol/L), MBOIA (0.5 mol/L), and MAIB (0.5 mol/L) gave benzene‐soluble copolymers despite a considerably high concentration of DVB as an excellent crosslinker. The yield and molecular weight of the resulting copolymers increased with time both at 70 and 80 °C and then leveled off because of initiator consumption. The homogeneous polymerization system involved electron spin resonance (ESR), observable nitrogen‐centered polymer radicals (MBOIA·) under the actual polymerization conditions. The MBOIA· concentration increased with time despite a homogeneous polymerization system, suggesting the formation of rigid hyperbranched polymers. A benzene solution of isolated copolymer also showed an ESR signal. The copolymer was soluble in acetone, toluene, chloroform, ethyl acetate, tetrahydrofuran, and N,N‐dimethylformamide but insoluble in n‐hexane, methanol, and dimethyl sulfoxide. MAIB fragments as high as 30–40 mol % were incorporated into the copolymers through initiation and primary radical termination, on the basis of which this polymerization was named the initiator‐fragment incorporation radical polymerization. MBOIA (13–16 mol%) was also incorporated into the copolymers through an opening of the C?N bond. The intrinsic viscosity of the copolymers was very low (0.08 dL/g), and the reduced viscosity was almost independent of the polymer concentration, supporting a hyperbranched structure of them. Gel permeation chromatography and multi‐angle laser light scattering and transmission electron microscopy revealed that the copolymer was formed as a hyperbranched nanoparticle. The thermal behavior of the copolymer was examined by dynamic thermogravimetry and differential scanning calorimetry. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3038–3047, 2003     

Synthesis of Poly(methyl methacrylate)-poly(poly(ethylene glycol) methacrylate)-polyisobutylene ABCBA Pentablock Copolymers by Combining Quasiliving Carbocationic and Atom Transfer Radical Polymerizations and Characterization Thereof

Novel, unique amphiphilic pentablock terpolymers consisting of the highly hydrophobic polyisobutylene (PIB) mid-segment attached to the hydrophilic combshaped poly(poly(ethylene glycol) methacrylate) (PPEGMA) polymacromonomer chains, which are coupled to poly(methyl methacrylate) (PMMA) outer segments were synthesized by the combination of quasiliving carbocationic polymerization and atom transfer radical polymerization (ATRP). First, a bifunctional PIB macroinitiator was prepared by quasiliving carbocationic polymerization and subsequent quantitative chain end derivatizations. Quasiliving ATRP of PEGMAs with different molecular weights (M_n = 188, 300 and 475 g/mol) led to triblock copolymers which were further reacted with MMA under ATRP conditions to obtain PMMA-PPEGMA-PIB-PPEGMA-PMMA ABCBA-type pentablock copolymers. It was found that slow initiation takes place between the PIB macroinitiator and PEGMA macromonomers with higher molecular weights via ATRP. ATRP of MMA with the resulting block copolymers composed of PIB and PPEGMA chain segments led to the desired block copolymers with high initiating efficiency. Investigations of the resulting pentablock copolymers by DSC, SAXS and phase mode AFM revealed that nanophase separation occurs in these new macromolecular structures with average domain distances of 11-14 nm, and local lamellar self-assembly takes place in the pentablocks with PPEGMA polymacromonomer segments of PEGMAs with M_n of 118 g/mol and 300 g/mol, while disordered nanophases are observed in the block copolymer with PEGMA having molecular weight of 475 g/mol. These new amphiphilic block copolymers composed of biocompatible chain segments can find applications in a variety of advanced fields.     

Rates of polymer formation and monomer consumption in the solution polymerization of trioxane catalyzed by BF3 · O(C2H5)2

In the solution polymerization of trioxane catalyzed by BF₃ · O(C₂H₅)₂ at 30°C. the amount of the methanol-insoluble polyoxymethylene is less than the amount of monomer consumed. This difference was much larger than the amount of formaldehyde determined in the polymerized system and could not also be explained in terms of the amount of the methanol-soluble oligomer. Tetraoxane was detected in large quantities by gas chromatography in the polymerized solution of trioxane. Therefore, the difference between the amounts of the methanol-insoluble polymer and the monomer consumed was ascribed partly to the formation of tetraoxane. In spite of the fact that tetraoxane was polymerized more easily than trioxane by BF₃ · O(C₂H₅)₂, an almost constant amount of tetraoxane was produced, independent of the kind of solvent and the polymer yield. This suggests the existence of an equilibrium concentration of tetraoxane. On the other hand, the formation of trioxane was observed in the solution polymerization of tetraoxane by BF₃ · O(C₂H₅)₂. This suggests that the formation of tetraoxane during the trioxane polymerization is due to a back-biting reaction in which the growing chain end of trioxane attacks the oxygen atom in its own chain with depolymerization of tetraoxane.     

Some linear and branched macromolecules by ring-opening polymerization

In the first part the ring-opening polymerization of some macrocyclic ether-acetals is briefly described. Of special interest are acetal polymers with functional groups, for instance C=C-double bonds. Appropriate unsaturated monomers and their polymerizability are discussed. The second part deals with the polymerization of oxazolines, substituted in 2- and/or 4-position. Branched polymers are obtained by copolymerization of 2-ethyl-2-oxazoline with 2-hexyl-2-oxazoline or 2-undecyl-2-oxazoline. The properties of the random copolymers and corresponding block copolymers are compared. By a “mixed mechanism technique” a block copolymer composed of a poly(tert -butyl methacrylate) block and a poly(phenyloxazoline) block was prepared. A new initiator system for the polymerization of oxazolines using alkyl chloroformates is introduced. The chloroformate of a trifunctional alcohol led to a three-arm star polymer. Telechelics with two chloroformate endgroups form ABA type block copolymers. Finally four chiral oxazolines are described and the influence of substitution in dioxolanes and oxazolines on the polymerizability is discussed.     

Cationic grafting from carbon black. VII. Grafting of polyacetals by cationic ring-opening polymerization of trioxane and 1,3-dioxolane initiated by CO+ClO4− groups on carbon black

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.     

Solubilization of cytochrome c in organic media with fluoroalkyl end-capped N-(1,1-dimethyl-3-oxobutyl)acrylamide oligomer: a new approach to fluorinated biocatalyst in organic media

Self-assembled molecular aggregates of fluoroalkyl end-capped N-(1,1-dimethyl-3-oxobutyl)acrylamide oligomer can solubilize cytochrome c in organic media such as methanol, although the corresponding non-fluorinated polymer cannot solubilize cytochrome c in organic media. Interestingly, the resulting fluorinated oligomer-cytochrome c aggregate was found to act effectively as a new fluorinated biocatalyst for the oxidation of pinacyanol chloride with hydrogen peroxide in the non-aqueous methanol.     

Retardation of spontaneous polymerization of formaldehyde by acidic substances

The stability of liquid formaldehyde produced by pyrolysis of α-polyoxymethylene was studied in connection with the presence of impurities in the monomer. Liquid monomer was divided into several fractions by means of the distillation. The stability of each fraction for polymerization is dependent on the order of fraction, that is, the monomer obtained in the early fractions of distillation was much more stable with regard to polymerization than later distillate. Analyses of the monomer fractions indicated that various impurities such as carbon dioxide, water, methanol, and methyl formate were present in the early monomer distillates. From the influence of these impurities on the stability of liquid formaldehyde, it was found that small amounts of carbon dioxide and hydrogen cyanide noticeably depressed the polymerization, and that with acetic acid and maleic anhydride the rate of polymerization decreased with small amounts of these compounds but increased with an excess of additive. On the other hand, the addition of these acidic substances did not affect the molecular weight of the polymer produced. From the fact that the acidic substance retards only the initiation of polymerization, it has been concluded that the spontaneous polymerization of formaldehyde in bulk or in toluene solution is initiated by an anionic species.     

聚醋酸乙烯酯和共聚物大分子引发剂引发异丁烯正离子接枝共聚合反应

以AIBN为引发剂,通过自由基聚合方法先合成一定分子量(Mn=1.9×104g mol)和分子量分布(MWD,Mw Mn<2.5)的聚醋酸乙烯酯(PVAc)和醋酸乙烯酯(VAc)与醋酸异丙烯酯(IPAc)的无规共聚物聚(PVIPA).再以PVAc或PVIPA作为大分子引发剂,与共引发剂TiCl4配合,引发异丁烯进行正离子接枝共聚反应,并分别考察大分子引发剂用量、TiCl4浓度以及添加剂2,6二叔丁基吡啶(DtBP)或2甲基吡啶(MPY)对异丁烯聚合转化率和PVIPA或PVAc引发效率的影响,并进一步表征接枝共聚物的微观结构与组成含量.实验结果表明,PVIPA和PVAc可引发异丁烯进行正离子接枝共聚反应,前者的引发效率高于后者.加入适量DtBP或MPY时,可不同程度地提高引发效率.DtBP对减少聚合体系中微量水的引发和提高PVAc引发效率的作用更为明显,引发效率可达90%以上,加入适量添加剂MPY时,PVIPA引发效率可达60%左右.适当增加大分子引发剂用量和TiCl4浓度,也可提高PVIPA的引发效率至接近70%.在合适的实验条件下,可以得到极性主链为PVIPA与非极性支链为聚异丁烯(35.2%mol)的接枝共聚物PVIPA g PIB,该接枝共聚物的Mn为3.7×104g mol,分布指数MWD为2.52,且PIB支链平均分子量约为5.4×103g mol.