Search

A suitable combination of the stability of propagating carbocation and the nucleophilicity of counterion is necessary in general for the formation of polymers with a bimodal molecular weight distribution: for styrene or p-chlorostyrene, less nucleophilic counterions (ClO4−, CF3SO3−) are suitable; for p-methyl-or p-methoxystryene, highly nucleophilic I3− or I− is required. In the styrene polymerization with ClO4− or CF3SO3− as counterion, the common-ion salt effect on the molecular weight distribution and the steric structure of the polymer suggest that two kinds of ion pairs as well as free ions are involved in the cationic polymerization. These species have been found to be different not only in reactivity in homopolymerization but also in monomer selectivity in copolymerization.

The lowering of degree of polymerization in cationic copolymerization was investigated for the isobutene–styrene copolymerizations in particular. In this system the simultaneous presence of a reactive isobutene cation and reactive styrene monomer acting as a chain transfer agent, a situation which cannot be visualized in homopolymerization, was proved to be responsible for giving low molecular weight copolymers. The ratios of rate constant for the monomer transfer reaction from isobutene cation to styrene monomer, a cross–transfer reaction, were determined kinetically. Carrying out the copolymerizations in solvents of different dielectric constant, in solvents of similar dielectric constant but of different solvating power, and with the Wichterle catalyst, and comparing the results with those by homogeneous catalyst, the polar and the nonpolar, possibly solvation effects of the solvent, and the effect of a heterogenity of catalyst on the crosstransfer reaction were investigated. A mechanism for the reaction was proposed. The choice of a comonomer or reaction conditions to minimize the cross-transfer reaction in isobutene copolymerization was discussed in the light of the information about the styrene-type monomer transfer reaction which has been reported previously by the present authors.

Synthesis of Multibranched Polymers by Linking Reactions of Linear Block Copolymers with Pendant Vinyl Groups by Conventional Radical Polymerization

Random copolymers with high molecular weights of indene and p-methylstyrene (pMeSt) were synthesized by cationic polymerization with trichloroacetic acid/ tin tetrachloride in CH 2 Cl 2 at low temperatures. When indene and pMeSt (1:1 v/v), for example, were polymerized at -40 °C, both monomers were consumed at very similar rates to give a copolymer with high molecular weight [number-average molecular weight (M n ): 8-9 x 10 4 ]. This is indeed quite unexpected behavior for the combination of these two monomers because pMeSt polymerized over 1000 times faster than indene in the homopolymerization under the reaction conditions previously described. The product copolymer of indene and pMeSt had a random monomer sequence in it that was confirmed by NMR analyses and thermal-property measurements. In sharp contrast with pMeSt, styrene and p-chlorostyrene, which have no electron-donating groups on the phenyl ring, led to low molecular weight polymers (M n < 10,000) in the copolymerization with indene (1:1 v/v).

The novel synthesis of EDTA-modified chitin/cellulose composite fibers is accomplished using dimethyl sulfoxide as the solvent, and the absorptive ability of the fibers for metal ions is examined by measuring absorption isotherms at different pHs. For some metal ions, the modified fibers show improved absorption powers compared with the parent fiber material. These composite fibers may be a reusable medium for metal ion removal and concentrations from an aqueous matrix.

Star-shaped polymers of isobutyl vinyl ether (IBVE) with a microgel core of an aliphatic divinyl ether (2) were synthesized in high yield on the basis of the living cationic polymerization with the HCl/ZnCl 2 initiating system. GPC analysis demonstrated that linear coupling products (two-armed polymers) and three-armed star polymers formed during the early stages of the linking reaction, and that subsequent coupling reactions between such low molecular weight star polymers gave star-shaped polymers with more arms The number of arms ranged from 5 to 22, which increased with increasing [2] 0 /[P * ] ratio and/or shortening the arm chain.

Cationic polymerization of n-butyl propenyl ether (BuPE; CH 3 CH= CHOBu, cis/trans = 64/36) was examined with the HCl-IBVE (isobutyl vinyl ether) adduct/ZnCl 2 initiating system at -15 ∼ -78 °C in nonpolar (hexane, toluene) and polar (dichloromethane) solvents, specifically focusing on the feasibility of its living polymerization. In contrast to alkyl vinyl ethers, the living nature of the growing species in the BuPE polymerization was sensitive to polymerization temperature and solvent. For example, living cationic polymerization of IBVE can be achieved even at 0 °C with HCl-IBVE/ZnCl 2 , whereas for BuPE whose β-methyl group may cause steric hindrance ideal living polymerization occurred only at -78 °C. Another interesting feature of this polymerization is that the polymerization rate in hexane is as large as in dichloromethane, much larger than in toluene. A new method in determining the ratio of the living growing ends to the deactivated ones was developed with a devised monomer-addition experiments, in which IBVE that can be polymerized in a living fashion below 0 °C was added to the almost completely polymerized solution of BuPE. The amount of the deactivated chain ends became small in hexane even at -40 °C in contrast to other solvents. Thus hexane turned out an excellent solvent for living cationic polymerization of BuPE.

産業廃棄物の利用という観点から,ビール工場で大量に排出されるビール仕込かす(大麦と副原料を糖化後,濾過したときの残さ)の吸着剤としての利用を試みた。用いた試料はビール仕込かすをふるい分けして得たタンパク質含有量が多い画分(Pr)とセルロースを多く含む画分(Hr)ならびにそれらの化学修飾体で,Hrはこれをジアルキルアミノエチル化し,Prはこれをアルカリ処理または塩酸処理して用いた。これらの基質に対する金属イオン(Pb2+,Cd2+,Fe3+,Cu2+,Ni2+)ならびに染料[酸性染料(C.I.Acid Orange 7,C.I.Acid Red 88)および塩基性染料(Methylene Blue)]の吸着性をバッチ法で調べた。Hrの酸性染料に対する吸着能は化学修飾によって,特にジエチルアミノエチル化によって著しく増加し,その増加度は前報に記した橋かけの効果をも大きく上回った。Prはこれをアルカリ処理したときには,金属イオンに対する吸着能も酸性染料に対する吸着能も,未処理の場合に比べて大幅に低下したが,これを塩酸処理することによって金属イオンに対する吸着能ならびにカチオン性の塩基性染料に対する吸着能を大きく向上させることができた。

In contrast to the common view, living cationic polymerization of p-methoxy- and p-t-butoxystyrenes proceeded in polar solvents such as EtNO 2 /CH 2 Cl 2 mixtures, and involvement of free ionic growing species therein was examined. For example, the two alkoxystyrenes were polymerized with the isobutyl vinyl ether-HCl adduct/ZnCl 2 initiating system at -15°C in such polar solvents as CH 2 Cl 2 or EtNO 2 / CH 2 Cl 2 [1/1 (v/v)], as well as toluene. The number average molecular weight (M n ) of the polymers increased in direct proportion to the monomer conversion, even after sequential monomer addition, and the molecular weight distribution (MWD) stayed very narrow throughout the reaction. In addition, the M n agreed with the calculated values, assuming that one adduct molecule generates one living polymer chain. In these polar media the addition of a common ion salt retarded the polymerization, indicating that dissociated ionic species are involved in the propagating reaction.

This paper discusses the nature of the living growing species in cationic polymerization from the viewpoint of the steric structure of poly(isobutyl vinyl ether) [poly(IBVE)]. At -78 °C, living polymerization was induced with the HCl-IBVE adduct (1)/ZnCl 2 system in a EtNO 2 /CH 2 Cl 2 mixture, whereas similar systems with EtAlCl 2 led to conventional cationic polymerization. In this polar medium, both systems gave polymers with very similar and low isotacticity (meso ≃ 56%), indicating that the propagating reaction is mediated by free ions. Thus, regardless of solvent polarity, or involvement of free ions or ion pairs, living cationic polymerization requires a suitably nucleophilic counteranion. As model reactions of the growing species, 1/ZnCl 2 and 1/EtAlCl 2 were directly analyzed by 1 H NMR spectroscopy.

Chitosan was crosslinked with glutaraldehyde in lactic acid, and the insoluble polymer obtained was examined for its ability to bind the acid dyes, C. I. Acid Orange 7 and Methyl Orange, in buffered solutions at pH's 5 and 7. The intrinsic and first binding constants and the number of binding sites for the binding of C. I. Acid Orange 7 by crosslinked chitosan were measured. Also the thermodynamicparameters accompanied by the binding were calculated. The first binding constant of C. I. Acid Orange 7 for crosslinked chitosan was larger than that for partially deacetylated chitin used as a control sample. This is mainly attributed to the difference of the number of binding sites between these two substrates. The binding ability of crosslinked chitosan for Methyl Orange was also larger than those of bovine serum albumin and poly (N-vinylpyrrolidone) showing large binding abilities for small molecules. The amount of C. I. Acid Orange 7 or Methyl Orange bound by chitosan was markedly lower than that of crosslinked chitosan in pH's 5 and 7, respectively. It is obvious that the affinity for the acid dyes is greatly increased by crosslinking through the entropy effect.

Copolymerizations of phenylacetylene with various polycyclic olefins (norbornene, dimethanooctahydronaphthalene, deltacyclene, norbornadiene, benzonorbornadiene, ethylidenebicycloheptene and trimethylsilylnorbornadiene) by WCl 6 - n -Bu 4 Sn catalyst were investigated. Phenylacetylene and these cycloolefins were simultaneously consumed. Formation of random copolymers was confirmed by the g.p.c. curves, u.v.-visible spectra and H-H COSY n.m.r. spectra of the copolymerization products. The copolymer composition curves were obtained and the monomer reactivity ratios were determined. The reactivities of these cycloolefins were close to or lower than that of phenylacetylene. Most of the r 1 × r 2 values were about unity or lower. In the case of norbornene-type monomers, the larger the ring strains of cycloolefins, the larger the reactivities to the phenylacetylene propagating end. Monocyclic olefins were scarcely or not consumed in the copolymerization with phenyl acetylene. kw]metathesis polymerization; phenylacetylene; cycloolefin

α-End-functionalized polymers and macromonomers of β-pinene were synthesized by living cationic isomerization polymerization in CH2Cl2 at −40°C initiated with the HCl adducts [1; CH3CH(OCH2CH2X)Cl; X = chloride (1a), acetate (1b), and methacrylate (1c)] of vinyl ethers carrying pendant substituents X that serve as terminal functionalities. In conjunction with TiCl3(OiPr) and nBu4NCl, these functionalized initiators led to living β-pinene polymerization where the carbon–chlorine bond of 1 was activated by TiCl3(OiPr). Similarly, end-functionalized poly(p-methylstyrene)-block-poly(β-pinene) were also obtained. 1H-NMR analysis showed that the polymers possess controlled molecular weights (DPn = [M]0/[1]0) and number-average end functionalities close to unity. The end-functionalized methacrylate-capped macromonomers form 1c were radically copolymerized with methyl methacrylate (MMA) to give graft copolymers carrying poly(β-pinene) or poly(p-methylstyrene)-block-poly(β-pinene) as graft chains attached to a PMMA backbone. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 1423–1430, 1997

The first example of living cationic isomerization polymerization of β-pinene was achieved with an initiating system that consists of the HCl−2-chloroethyl vinyl ether adduct [1a; CH3CH(OCH2CH2Cl)Cl] and isopropoxytitanium trichloride [TiCl3(OiPr)] in the presence of tetra-n-butylammonium chloride (nBu4NCl) in CH2Cl2 at −40 and −78 °C. The number-average molecular weight of the polymers (Mn ≤ 5 × 103) increased in direct proportion to monomer conversion, and the molecular weight distribution of the polymers was relatively narrow (Mw/Mn ∼ 1.3). The living nature of the polymerization was further demonstrated by monomer-addition experiments. A similar living polymerization was also feasible with the HCl−styrene adduct or 1-phenylethyl chloride [1b; CH3CH(Ph)Cl] in conjunction with TiCl3(OiPr) and nBu4NCl. 1H NMR analysis of the polymers from 1a showed that 1a serves as an initiator and generates poly(β-pinene) chains consisting of the 1-(2-chloroethoxy)ethyl head group, a tert-chloride tail group, and is...

1-Phenyl-2-[m-(trimethylgermyl)phenyl]acetylene (m-Me3GeDPA) and 1-phenyl-2-[p-(trimethylgermyl)phenyl]acetylene (p-Me3GeDPA) polymerized with TaCl5–cocatalyst systems to provide in high yields new polymers having weight-average molecular weights over 1 × 106. Poly(m-Me3GeDPA) was a yellow solid, which completely dissolved in toluene, chloroform, etc., to form a tough film by solution casting. Poly(p-Me3GeDPA) was also a yellow solid and partly insoluble in any solvents. The onset temperatures of weight loss for these polymers in the thermogravimetric analysis in air were as high as ca. 400°C. The oxygen permeability coefficient of poly(m-Me3GeDPA) was 1100 barrers (25°C), which is about twice that of poly(dimethylsiloxane). © 1996 John Wiley & Sons, Inc.

The polymerization of β-pinene with the AlCl3/SbCl3 binary catalyst was investigated in toluene at −40°C and was compared with that of α-pinene. The polymerization of β-pinene with AlCl3 alone was very rapid and retarded on addition of SbCl3, in sharp contrast to that of α-pinene where added SbCl3 remarkably accelerated it to give relatively high molecular weight oligomers. Attempted copolymerization of the two isomers with the binary catalyst, in turn, induced their parallel homopolymerizations, indicating that the copolymerization was difficult due to the large difference in reactivity. The homopolymerizations with AlCl3/SbCl3 were not seriously affected by a sterically hindered base, 2,6-di-tert-butyl-4-methylpyridine (DTBMP); the initiating species, therefore, would be different in nature from a proton. © 1996 John Wiley & Sons, Inc.

(p-tert-Butyl-o,o-dimethylphenyl)acetylene (BDMPA) polymerized in high yields in the presence of W and Mo catalysts. Especially the W(CO) 6 -CCl 4 -hν catalyst quantitatively produced a polymer totally soluble in toluene and chloroform. The weight-average molecular weight of this polymer exceeded 2 x 10 6 . Poly(BDMPA) was a dark brown solid, and had alternating double bonds along the main chain. The weight loss of the polymer in air occurred only above 300°C, indicating a fairly high thermal stability. A free-standing film could be fabricated by solution casting. The electrical conductivity of the polymer at 25°C was 1 X 10 -l3 S cm -l . The oxygen permeability coefficient and the separation factor of O 2 vs. N 2 of the polymer at 25°C were 67 barrers and 3.2, respectively.

By the polymer coupling reaction with a tetrafunctional silyl enol ether [1; C{CH2OC6H4C(OSiMe3)CH2}4], amphiphilic tetraarmed star polymers (6) with α-methylstyrene−2-hydroxyethyl vinyl ether (αMeSt−HOVE) block arm chains have been synthesized: C{CH2OC6H4COCH2−[CH(OCH2CH2OH)CH2]n−[C(CH3)(C6H5)CH2]m−}4. The synthesis consisted of the following steps: (i) the sequential living cationic polymerization of αMeSt and 2-[(tert-butyldimethylsilyl)oxy]ethyl vinyl ether (SiVE) into an αMeSt−SiVE living block copolymer (4); (ii) the coupling of four chains of 4 with the quencher 1 into a tetraarmed polymer (5); and (iii) the transformation of the poly(SiVE) segment into the poly(HOVE) chain by the fluoride-catalyzed deprotection. In step i the living polymerization was carried out at −78 °C in methylene chloride with a binary initiating system comprising tin tetrabromide and the hydrogen chloride adduct of 2-chloroethyl vinyl ether. After step iii, the tetraarmed amphiphile 6 (αMeSt/HOVE = 27/27 in n in each arm)...

Stereospecificity of the polymerization of tert-butylacetylene by Mo-based catalysts was investigated. The polymer obtained by the MoOCl4−n-Bu4Sn system just after complete monomer consumption had an all-cis structure. However, the stereoregularity decreased when the polymerization was allowed to stand further. These findings indicate that, though the propagation reaction proceeds stereospecifically, the geometric isomerization of polymer lowers stereoregularity. This isomerization was catalyzed by several acids as well as by polymerization catalysts and, hence, is an acid-catalyzed reaction. Highly stereoregular polymer could be obtained by accelerating polymerization (by use of cocatalysts) and/or by decelerating isomerization (by use of cocatalysts, poor solvents of the polymer, or the less acidic Mo(CO)6-based catalyst and by polymerization at low temperatures).

Cationic polymerizations of p-chlorostyrene (pClSt), p-(chloromethyl)styrene (pCMS), and p-(acetoxymethyl)styrene (pAcOMS) were examined with HCl−vinyl monomer adduct (1; CH3CH(R)Cl; 1a: R = Ph, 1b: R = OCH2CH2Cl)/SnX4 initiating systems in the presence or absence of an ammonium salt. Living polymers were obtained from pClSt using the 1-phenylethyl chloride (1a)/SnCl4/nBu4NCl initiating system in CH2Cl2 at 0 °C. Thus, without the ammonium salt, the 1a/SnCl4 system led to a conventional cationic polymerization to give polymers with bimodal molecular weight distributions (MWDs), but in the presence of nBu4NCl, polymers with unimodal and very narrow MWDs (Mw/Mn ≈ 1.1) were obtained. The number-average molecular weight (Mn; by 1H NMR) of the polymers increased in direct proportion to conversion, agreed with the calculated value assuming that one polymer chain forms per molecule of 1a, and further increased on addition of a fresh pClSt feed into a completely polymerized solution. More important, living po...

Star-shaped polymers (4) that consist of poly(p-alkoxystyrene) arms and a microgel core of a divinyl compound (1b) were synthesized in high yield (>95%) on the basis of the living cationic polymerization with the HI/ZnI2 initiating system. For example, the polymerization of p-methoxystyrene (pMOS) with HI/ZnI2 at −15 °C in methylene chloride led to a living polymer, which was subsequently allowed to react with a small amount of the linking agent 1b [CH2CHC6H4O(CH2)3OC6H4CHCH2] to give star-shaped polymers 4, soluble in common organic solvents including chloroform, methylene chloride, and THF. The Mw (by light scattering) of 4 ranged from 5 × 104 to 60 × 104, and the number of arms from 7 to 50 per molecule, which increased with increasing [1b]0/[living end] ratio. Similar results were obtained with p-tert-butoxystyrene having a bulkier substituent than pMOS. In contrast to the bis(alkoxystyrene)-type compound 1b, the use of a bifunctional vinyl ether [1a; CH2CHOCH2CH2OC6H4C(CH3)2C6H4OCH2CH2OCHCH2] as a l...

Tri- and tetraarmed polymers (3-P and 4-P) of α-methylstyrene (αMeSt) and their end-functionalized versions (12) [R4-mC{CH2OC6H4COCH2−(αMeSt)n−CHMeOCH2CH2−X}m (Me = CH3); arm number m = 3 (R = Me), 4; X = Cl, OCOMe, OCOCMe=CH2] have been synthesized by coupling reactions of living poly(αMeSt) with multifunctional silyl enol ethers [R4-mC{CH2OC6H4C(OSiMe3)CH2}m; 3, m = 3, R = Me; 4, m = 4]. The living poly(αMeSt) was prepared by living cationic polymerization in methylene chloride solvent at −78 °C with the hydrogen chloride−vinyl ether adduct [Cl−CHMe(OCH2CH2−X)] as initiator in conjunction with tin tetrabromide (SnBr4). Subsequently, the living chains were allowed to react with 3 or 4 in the presence of N-ethylpiperidine to give the target multiarmed polymers in high yield (>90%). Specifically for αMeSt, it proved crucial that N-ethylpiperidine and similar nucleophiles should be added into the living polymer solution for its efficient coupling to occur. In the end-functionalized polymers (12), each of th...

Titanium(IV)-based new initiating systems for living cationic polymerization of isobutyl vinyl ether (IBVE) have been developed by using a series of isopropoxytitanium chlorides [TiCl 4-n (OiPr) n ; n = 0-4] in conjunction with the IBVE-HCl adduct in CH 2 Cl 2 at -15 °C. The 1 H and 13 C NMR analysis of the titanium compounds showed that their Lewis acidity decreased with the increasing number (n) of isopropoxyl groups and affected the polymerizations accordingly. For example, TiCl 4 and TiCl 3 (OiPr), the strongest Lewis acids among the five, induced very rapid polymerizations to give polymers with broad molecular weight distributions (MWDs) (M w /M n ∼1.6). In contrast, the reaction rate with TiCl 2 (OiPr) 2 , a weaker Lewis acid, was moderate. The MWDs of the polymers were narrow throughout the reaction (M w /M n < 1.2), and the number average molecular weights increased in direct proportion to monomer conversion. The polymerization with TiCl(OiPr) 3 was slower, and the MWDs became slightly broader. No polymer was obtained with a much weaker Lewis acid, Ti(OiPr) 4 . Another modified titanium chloride, TiCl 2 (OPh) 2 , also led to a controlled polymerization of IBVE which is similar to the one with TiCl 2 (OiPr) 2 . These results indicate that living cationic polymerizations of IBVE can be achieved by controlling the Lewis acidity of the titanium(IV) activators with electron-donating groups.

Model reactions of the living cationic polymerization of isobutyl vinyl ether (IBVE) with HCl-IBVE adduct [1: CH 3 CH(OiBu)Cl]/SnCl 4 initiating system were directly analyzed by 13 C and 1 H NMR spectroscopy in CD 2 Cl 2 at -78 o C to demonstrate the formation of carbocation from 1. Under the polymerization condition, the 1/SnCl 4 initiating system gave nonliving polymers, but in the presence of nBu 4 NCl, it induced living polymerization, and the spectral data were closely correlated with the salt-assisted transition from nonliving to living polymerization. For example, upon mixing SnCl 4 with 1, the α-methine and the pendant methylene absorptions of 1 shifted remarkably downfield (e.g., up to 227 ppm in 13 C NMR for the former), and the extent of the downfield shifts increased with increasing SnCl 4 concentration. On further addition of the salt, the downfield signals returned to the original upfield positions close to those for the covalent adduct 1. Thus, these changes and coupling constant ( 1 J CH ) analysis demonstrated that 1/SnCl 4 generates an sp 2 -type carbocationic species that is in a rapid and dynamic exchange equilibrium with the covalent precursor 1, and adding nBu 4 NCl suppresses the growing carbocation, thereby leading to living cationic polymerization

Amphiphilic tetraarmed star poly(vinyl ethers), where each arm carries alkyl (hydrophobic) and alcohol (hydrophilic) pendant groups, have been synthesized by the coupling reaction of AB-block living poly(vinyl ethers) (4; arm chain) with a tetrafunctional silyl enol ether 1, C[CH 2 OC 6 H 4 -p-C(OSiMe 3 )=CH 2 ] 4 . The living arm chaise 4 were prepared by the sequential living cationic polymerization of an alkyl vinyl ether (CH 2 =CHOR 1 ; R 1 =iBu, CH 2 CH 2 Cl) and a fuctionalized vinyl ether (CH 2 =HOCH 2 -CH 2 R 2 ; R 2 =OCOCH 3 , OSi t BuMe 2 ) with hydrogen chloride/zinc chloride initiating system in methylene chloride at -15 o C. The treatment of 4 with the silyl enol ether 1 led to tetraarmed block copolyiners 5. The yield of 5 (93-73%) depended on the structure and the polymerization sequence of the monomer pair for the arm chain 4. The best result (93% yield) was obtained with the AB-block polymer of 2-chloroethyl vinyl ether (R 1 =CH 2 CH 2 Cl; CEVE) and 2-acetoxyethyl vinyl ether (R 2 =OCOCH 3 ; AcOVE) where CEVE has polymerized first. Separate coupling experiments with the homopolymers of these vinyl ethers showed that the coupling yield was higher for monomers with less bulky pendant groups. Subsequent quantitative deprotections of the acetoxy of tert-butyldimethylsilyl groups in 5 into hydroxyl groups gave the amphiphilic tetraarmed polymers 6. By changing the polymerization sequence of the monomer pair, the hydrophilic polyalcohol segments could be placed either inside or outside the tetraarmed structure. For pairs of such inner- and outer-alcohol versions with identical segmental compositions, solubility and arm-chain conformation (by 1 H NMR) were compared

Direct 1H, 13C and 19F NMR spectroscopic analysis was carried out on the carbocationic intermediate generated in the interaction of tin(IV) chloride (SnCl4) with the adduct [4, CH3CH(OiBu)OCOCF3] of isobutyl vinyl ether (IBVE) and trifluoroacetic acid (CF3CO2H), either in the presence or in the absence of tetrabutylammonium chloride. The reactions were to mimic the living cationic polymerization of IBVE by the 4–SnCl4 initiating system (with added nBu4NCl) that was also found in this study. In CD2Cl2 solvent at −78°C, the 1H and 13C NMR analysis revealed the formation of a carbocationic intermediate [CH3C+H(OiBu)] that is in a rapid exchange equilibrium with the covalent counterpart 4. For the first time, the cation formation was further supported by 19F NMR analysis on the counteranionic part (CF3COO−) in 4, where, with SnCl4, the CF3 group gave a broadened signal that appeared clearly downfield relative to that in the covalent form. These and other results, which are in close correlation with the corresponding polymerizations, demonstrated the following: (i) the SnCl4-assisted generation of carbocationic species from the covalent ester 4; (ii) a rapid exchange between the cation and its covalent precursor 4; (iii) the relatively high cationic concentration in the salt-free system, where no living polymerization occurs; and (iv) the effective suppression of the cationic species in the presence of the salt, which proved to be the prime key factor for living polymerization.

The sizes and shapes of star-shaped poly(vinyl ether)s, prepared by living cationic polymerization, were studied by dynamic light scattering and molecular mechanics-based computer simulation. The hydrodynamic radii (Rh) of star poly(isobutyl vinyl ether)s (4a; Mw = 2.2 × 104 − 1.7 × 105) determined by dynamic light scattering were in the range from 30 to 90 A in tetrahydrofuran or ethyl acetate. Consistent with the expected multiarmed architecture of 4a, the radius for a given number (f) of arms per molecule increased with the degree of polymerization [DP(arm)] of the arms, and for a fixed DP(arm), the radius increased with f. The relationship between arm number f and the “shrinking” factor h [Rh(star)/Rh(linear)] was consistent with multibranched structures for the star polymers. These results are supported by those for the molecular weight itself; the apparent weight-average molecular weights by size-exclusion chromatography are less than the corresponding absolute values by static light scattering. The dependence of h on f suggests some degree of asymmetry in the star shape. Similar results were also obtained by the computer simulation of potential energy-minimized conformations of the arms, which implied almost spherical but slightly asymmetric shapes. The computer simulation also demonstrated that the star polymer (4b) with pendant hydroxyl groups in the arms is smaller in size than the corresponding alkyl (isobutyl) (4a) with the identical arm number and arm degree of polymerization. © 1995 John Wiley & Sons, Inc.

3-(N-Carbazolyl)-1-propyne polymerized with MoCl5- and WCl6-based catalysts to produce a polymer in high yields. The MoCl5 and MoCl5-n-Bu4Sn catalysts were the most effective (the systems solidified immediately after initiation of polymerization with these catalysts). The product polymer was a yellow solid insoluble in any solvent. Copolymerization of the present monomer with tert-butylacetylene by MoCl5-n-Bu4Sn produced a copolymer; it had a high molecular weight (Mw 350,000), completely dissolved in toluene, CHCl3 etc, and formed a free-standing film by solution casting. ω-N-Carbazolyl-1-hexyne and-1-octyne produced toluene-insoluble polymers with WCl6-Ph4Sn.

Hole resonance among more than two chromophores for the radical cationic carbazole (CZ) group of poly(N-vinylcarbazole) (PVCZ) in solution was shown by the radical ion transfer method and charge resonance (CR) band measurements. The sample was PVCZ with its oligomers (degree of polymerization (DP) = 2-100). The hole transfer rate from the radical cationic CZ of the oligomers to a 2,5-dimethoxyaniline, which has a lower ionization potential than the CZ chromophore, decreased with an increase in the oligomer molecular weight due to the hole resonance among neighboring chromophores. Thus, the stabilization energy of N-vinylcarbazole oligomers increases with increase in DP. The peak position of the CR band can be a good measure of the degree of charge resonance. The peak wavelength of the CR band was red-shifted for the larger molecular weight oligomers. This shift also suggested the existence of charge resonance in PVCZ among more than two CZ chromophores.

Novel phenylacetylene (PA) monomers, which have o-silylmethyl groups of different bulkinesses, i.e., o-Me 3 SiCH 2 PA, o-Et 3 SiCH 2 PA, and o-t-BuMe 2 Si-CH 2 PA, polymerized with W and Mo catalysts in high yields. The MoCl 5 -Ph 4 Sn catalyst achieved the highest weight-average molecular weights (M w 7×10 5 -12×10 5 ), and the M w increased as the ortho-substituent became bulkier (e.g., M w of o-t-BuMe 2 SiCH 2 PA:12×10 5 ). These monomers polymerized in a living fashion by the MoOCl 4 -n-Bu 4 Sn-EtOH catalyst. The resulting polymers were soluble in common solvents

Polymerization of (o-methylphenyl)acetylene (o-MePA) by MoOCl4-n-Bu4Sn-EtOH catalyst in toluene at 0°C provided a cis-rich living polymer; cis 77%, M w/M n=1.21. The polymerization at -30°C gave results similar to those for 0°C, whereas the polymer obtained at 30°C exhibited a broader molecular weight distribution (MWD) and a lower cis content. Among several organotin compounds, only n-Bu4Sn was effective for the living polymerization of o-MePA. The bulkier the alkyl group of alcohols as the third catalyst component, the broader the MWD of the polymer, while the geometrical structure was not affected by the alcohols.

1-(1-Naphthyl)-1-propyne polymerized in the presence of NbCl5–cocatalyst systems to give virtually selectively a new polymer ca. 3 × 105) in high yields. Catalysts based on TaCl5 produced mixtures of the polymer and cyclotrimers. The polymer was a pale-yellow solid soluble in various organic solvents (e.g., toluene, CHCl3), and formed a free-standing film on solution casting. The onset temperature of the weight loss of the polymer in air was ca. 340 °C, which is higher than that (280 °C) of poly(1-phenyl-1-propyne) [poly(1-PP)]. The oxygen permeability coefficient at 25 °C was 80 barrers and one order of magnitude higher than that of poly(1-PP). These results are explicable in terms of the steric effects of the 1-naphthyl group.

Telechelic (8) and end-functionalized four-arm star polymers (9) were synthesized through the coupling reactions of end-functionalized living poly(isobutyl vinyl ether) (5;DPn ∼ 10) with the bi-and tetrafunctional silyl enol ethers, H4-nC[CH2OC6H4C(OSiMe3) = CH2]n (3: n = 2; 4: n = 4). The precursor polymers 5 were prepared by living cationic polymerization with functionalized initiators, CH3CH(Cl)OCH2CH2X(6), in conjunction with zinc chloride in methylene chloride at −15°C. The initiators 6 were obtained by the addition of hydrogen chloride gas to vinyl ethers bearing pendant functional groups X, including acetoxy [OC(O)CH3], styryl (OCH2C6H4-p-CH = CH2), and methacryloyl [OC(O)C(CH3) = CH2]. The coupling reactions with 3 and 4 in methylene chloride at −15°C for 24 h afforded the end-functionalized multiarmed polymers (8 and 9) in high yield (>91%), where those with styryl or methacryloyl groups are new multifunctional macromonomers. © 1994 John Wiley & Sons, Inc.

The end-functionalization of living polymers with bases (methanol, benzylamine, diethyl sodiomalonate, and sodium methoxide) and organosilicon compounds [X Si(CH3)3;X : CH2C(CH3)COO, CH3COO, CH2CHCH2, C6H5] was investigated in the living cationic polymerization of styrene initiated with the 1-phenylethyl chloride/SnCl4/nBu4NCl system in CH2Cl2 at −15°C. The four bases and C6H5SiMe3, independent of their structures, were apparently incapable of reacting with the living end and invariably led to polystyrenes with the ω-end chlorine [∼ ∼ ∼ CH2CH(Ph)Cl] originated from the initiating system. The number-average end-functionality (Fn) of the chloride, determined by 1H-NMR, was close to unity (Fn > 0.9). The presence of chlorine in the polymer was also confirmed by elemental analysis. In contrast, the quenching by the trimethylsilyl compounds with X = methacryloxy, acetoxy, and allyl gave ω-end-functionalized polystyrenes with the corresponding terminal groups (X) for which the Fn values were close to unity (Fn > 0.9). The effects of the structure of silyl compounds on end-capping are also discussed. © 1994 John Wiley & Sons, Inc.

The polymerization of three diarylacetylenes, namely 1-( p -benzylphenyl)-2-phenylacetylene ( p -BzDPA), 1-( p -phenylphenyl)-2-phenylacetylene and 1-(β-naphthyl)-2-phenylacetylene, was examined. These monomers polymerized in good yields with TaCl 5 -cocatalyst systems. Poly( p -BzDPA) was soluble in various organic solvents and had high molecular weights of 6 × 10 5 −9 × 10 5 according to gel permeation chromatography. In contrast, the other two polymers were insoluble in all solvents. All these polymers had fairly good thermal stability in air (their onset temperatures of weight loss in air were 330–450°C). The oxygen permeability coefficient of poly( p -BzDPA) at 25°C was 18 barrers, which was close to that of natural rubber (23 barrers).

1-(p-t-Butylphenyl)-2-phenylacetylene and 1-(p-n-butylphenyl)-2-phenylacetylene were polymerized in catalytic systems based on TaCl5 to give new polymers in high yields. These monomers were more reactive than diphenylacetylene (DPA) in copolymerization. Unlike poly (DPA), the present polymers were soluble in toluene, CHCl3, etc. owing to the high configurational entropy induced by the para-substituents. Their relative weight-average molecular weights determined by GPC were in the range of 6 × 105–36 × 105, and films could be obtained by solution casting. These polymers were fairly thermally stable, as seen from their high onset temperatures (320–380°C) of weight loss in TGA in air. The oxygen permeability coefficient of the polymer with t-Bu group was 1100 barrers, the highest among those of all the hydrocarbon polymers. © 1994 John Wiley & Sons, Inc.

Both AB and BA block copolymers of α-methylstyrene (αMeSt) and 2-chloroethyl vinyl ether (CEVE) were synthesized by the sequential living cationic polymerization initiated with the HCl-CEVE adduct (1a)/SnBr4 system in CH2Cl2 at -78°C. αMeSt-CEVE (AB) block copolymers with narrow molecular weight distributions ([Mbar]w/[Mbar]n ∼ 1.15) were obtained when αMeSt was polymerized first, followed by addition of CEVE to the resulting αMeSt living polymer solution. The reverse order of monomer addition, from CEVE to αMeSt, also led to a BA-type block copolymer. In the polymerization of a mixture of the two monomers, almost random copolymers were obtained. Living polymerizations of αMeSt were also induced with functional initiating systems, HCl-functionalized vinyl ether adducts (1b-1d)/SnBr4, to give end-function-alized poly(αMeSt)s with a methacrylate, an acetate, or a phthalimide terminal.

(2-Methyl-5-tert-butylphenyl)acetylene (2Me5tBuPA) polymerized in the presence of MoCl5-n-Bu4Sn catalyst in 1,4-dioxane to give a high molecular weight polymer \((\overline M _w {\text{ }}8x10^5 )\). Not only MoCl5- but also WCl6-based catalysts were effective. The polymer obtained was a dark brown solid, soluble in organic solvents such as toluene and CHCl3, and formed a freestanding film by solution casting. The onset temperature of weight loss of the polymer in air was 260 °C. Its oxygen permeability coefficient was 43 barrers, which is twice that of natural rubber. Differences from the results (usually lower molecular weight, not film-forming, and thermally less stable) of both poly(phenylacetylene) and poly[o-methylphenyl)acetylene] are attributable to the synergistic steric effect of the o-methyl and m-tert-butyl groups.

AB block copolymers of methylvinyl ether (MVE) and styrene were synthesized by the sequential living cationic polymerization. The first-stage polymerization was with MVE and was initiated in CH 2 Cl 2 solvent at -78°C with the adduct [1; CH 3 CH(OiBu)Cl] of HCl and isobutyl vinyl ether (IBVE) as an initiator in conjunction with SnCl 4 Lewis acid activator and nBu 4 NCl. To the solutions of the resultant living poly(MVE) at -78°C (conversion ∼100%) were sequentially added styrene and a mixture of SnCl 4 and the salt

The polymerization of tert-butylacetylene(tBA) by the MoOCl 4 -n-Bu 4 Sn-EtOH (1:1:1) catalyst led to living and stereoregular polymers with narrow molecular weight distributions (M w /M n = 1.12; cis 97%). The living nature of this polymerization was confirmed by the fact that, in toluene at 0 and -30°C, the M n of the polymer increases in direct proportion to monomer consumption, while the molecular weight distribution remains narrow. Similar but some what inferior results were obtained with the MoCl 5 -n-Bu 4 n-EtOH (1:1:1) system (M w /M n = 1.24; cis 90%)

Tri- and tetrafunctional silyl enol ethers, Me 4-n C[CH 2 OC 6 H 4 C(OSiMe 3 )=CH 2 ] n (3: n=3; 4: n=4), proved efficient multifunctional coupling agent for the living polymer of isobutyl vinyl ether (IBVE) prepared by the HCl/ZnCl 2 initiating system at -15°C in CH 2 Cl 2 . The silyl enol ethers were readily synthesized by the silyl enolation of the corresponding multifunctional acetophenones. Upon the coupling reactions, the molecular weight M n of the products increased in accordance with the multiplicity of the coupling agents

A new catalyst system prepared by UV irradiation of a toluene solution of W(CO)6 and a Lewis acid polymerized phenylacetylene (e.g., polymer yield 50%, Mn 5.0×104 with SnCl4 (0.5 equivalent to W(CO)6) as Lewis acid). This catalyst afforded high molecular weight polymers Mn 4×105 − 5×105) from phenylacetylenes with ortho-substituents (e.g., o-Me3Si and o-CF3). The Mo(CO)6-based counterpart was rather effective to acetylenes having electron-withdrawing groups (e.g., ClC ≡ Cph). Polymerization of phenylacetylene occurred as well when SnCl4 was added after UV irradiation of a toluene solution of W(CO)6 and the monomer; this suggests that the polymerization proceeds via metal carbenes having coordinated SnCl4.

Polymerization of 1-phenyl-2-(p-phenoxyphenyl)acetylene (p-PhODPA), 1-phenyl-2-(p-methoxyphenyl)acetylene, and 1-phenyl-2-(p-n-butoxyphenyl)acetylene was examined. These monomers polymerized with TaCl5-n-Bu4Sn to give methanol-insoluble polymers in over 60% yields. Poly(p-PhODPA) was a yellow solid completely soluble in toluene, CHCl3, etc., and its weight-average molecular weight was about 1.0x106 or higher. This polymer was thermally very stable (the onset temperature of weight loss in TGA in air was 420 °C). Its oxygen permeability coefficient (Po2) was 37 barrers (Po2/Pn2 2.2) and similar to that of natural rubber. In contrast, the other two polymers did not completely dissolve in any organic solvent, and their thermal stability was lower.

(o-Alkylphenyl)acetylenes (alkyl: Et, n-Bu, n-C6H13, n-C8H17, and iso-Pr) polymerized in high yields with W and Mo catalysts. MoCl5-based catalysts, which are not very active to phenylacetylene (PA), exhibited high activity like the WCl6 counterparts. The weight-average molecular weights (Mw) of the polymers having o-n-alkyl groups were in the range 2×104—55×104, being similar to or slightly higher than those of poly(PA), while the highest Mw value of poly(o-iso-Pr-phenylacetylene) [poly(iso-PrPA)] reached 1×106. The formed polymers were dark red, and had the structure –[- CH = C(C6H4-alkyl) -]n–. They were thermally more stable than poly(PA) according to the thermogravimetric analysis. The polymers with long o-n-alkyl groups were soluble in aliphatic solvents (e.g., hexane) unlike poly(PA), and their softening points were lower. Poly(o-iso-PrPA) was film-forming, and fairly gas-permeable (PO2, 27 barrers, PO2/PN2 2.2).

A series of multiarmed polymers with terminal functional groups have been synthesized on the basis of living cationic polymerizations of vinyl ethers and p-alkoxystyrenes. The syntheses were performed by two methods, one via living polymerizations with new multifunctional initiating systems followed by endcapping of the resultant multifunctional living polymers, and the other using designed silyl enol ethers as multifunctional terminators (coupling agents) that combine two to four end- functionalized linear living polymers. These two methodologies thus led to telechelic and 3- or 4-arm star polymers and macromonomers with hydroxyl, acetate, methacrylate, and styryl end functionalities.