Tomoo Shiomi

13C NMR determination of substituent distribution in carboxymethylcellulose by use of its peresterified derivatives

Abstract The distribution of carboxymethyl groups in a series of sodium O-(carboxymethyl)cellulose (CMC) samples was determined by 13C NMR analysis of their peresterified derivatives. Thus sodium carboxymethyl groups were first converted into methyl ester groups by treatment with dimethyl sulfate in Me2SO at 40 °C, to produce methyl-esterified CMC (MCMC). Subsequent propanoation of unsubstituted hydroxyl groups by propanoic anhydride in N,N-dimethyl-acetamide-LiCl at 100 °C in the presence of DMAP produced propanoated MCMC (PMCMC), which was readily soluble in Me2SO-d6 regardless of the degrees of substitution. The propanoyl carbonyl carbon signal in a series of PMCMC samples was found to resolve into three peaks in Me2SO-d6 at 100 °C, corresponding to the position of the substitution position (2, 3, and 6) on the glucose residue, permitting subsequent determination of the distribution pattern of carboxymethyl groups in the parent CMC samples.

Synthesis of α-maleimide-ω-dienyl heterotelechelic poly(methyl methacrylate) and its cyclization by the intramolecular Diels-Alder reaction

The synthesis of heterotelechelic poly(methyl methacrylate) (PMMA) containing α-maleimide-ω-dienyl end-groups and its subsequent intramolecular cyclization are described. The anionic polymerization of methyl methacrylate was carried out with 3-tert-butyldimethylsilyloxypropyl-1-lithium and 5-bromo-1,3-pentadiene as the initiator and terminator, respectively, to synthesize α-hydroxy-ω-dienyl-PMMA. The introduction of the maleimide group to the α chain end by the reaction of the sodium salt of the polymer with N-(3-chloromethylphenyl)-maleimide or N-(3-bromomethylphenyl)-maleimide was not successful because of the nucleophilic addition of alkoxide to the carboncarbon double bond of the maleimide group. When 4,4′-bismaleimidediphenylether was allowed to react with the alkoxide, the aimed α-maleimide-ω-dienyl-PMMA was obtained in a good yield. Ring closure by the intramolecular Diels–Alder reaction was carried out by the heating of the dilute polymer solution in tetrahydrofuran.

UCST and LCST behaviour in polymer blends containing poly(methyl methacrylate-statstyrene)

Abstract Miscibility behaviour was investigated for the blends of homopolymer A with the random copolymer consisting of two components B and C, where the A homopolymer is miscible with homopolymer B but immiscible with homopolymer C. The copolymer employed was poly(methyl methacrylate-stat-styrene) (MMA·S), and the homopolymers were polystyrene (PS), poly(vinyl methyl ether) (PVME), and poly(ethylene oxide) (PEO) or poly(ethylene glycol) (PEG), where PS is immiscible with MMA homopolymer, PVME is miscibel with S but immiscible with MMA, and PEO or PEG is miscible with MMA but immiscible with S. UCST-type miscibility was observed for the PEO/MMA·S blends though the homopolymer blends PEO/PMMA had been reported to be of LCST-type. UCST-type miscibility was found for PS/MMA·S as well. On the other hand, PVME/MMA·S showed LCST-type miscibility with miscibility window-like behaviour. Such contrasting miscibility behaviour, i.e. appearances of UCST and LCST, for a series of MMA·S copolymer blends was discussed on the basis of the Flory-Patterson free volume theory. As a result, it was suggested that contribution of the free volume term decreases for PEO/MMA·S (UCST type), increases for PVME/MMA·S (LCST type) and is little changed for PS/MMA·S (UCST type), compared with that for the respective miscible component pairs, PEO/MMA, PVME/S and PS/S. Furthermore, the Flory-Huggins χ parameters between different components were estimated as a temperature-dependent function from dependence of miscibility on the copolymer composition in these blends. In this estimation, the χ parameters determined for PVME/PS and PEO/PMMA by Han et al. and Ito et al. , respectively, using neutron scattering technique were used as a standard. The miscible/immiscible boundaries drawn using the χ parameters obtained reproduced well the experimental results of the dependence of miscibility on the molecular weight as well as on the copolymer composition. Thus, it was shown that the χ parameters for immiscible pairs such as PS/PMMA, PEO/PS and PVME/PMMA can be evaluated by use of the blend type A/B·C dealt with here.

Dependence of swelling degree on solvent composition of two-component copolymer networks in mixed solvents

The two-component copolymer networks, polystyrene/poly(tetrahydrofuran) and poly(methyl methacrylate)/ poly(tetrahydrofuran), were synthesized and their swelling behaviour was investigated in three kinds of mixed solvents, which were chosen so as to contrast with one another in respect of solubility of the component polymers. These copolymer networks exhibited three types of solvent composition dependence of the swelling degree, corresponding to the three kinds of mixed solvents: existence of a maximum, a monotonic change, and a significant change having an inflection point, in the same manner as the polystyrene/ poly(dimethylsiloxane) copolymer networks reported by us previously. These three types of swelling behaviour were analysed thermodynamically on the basis of swelling equations. For this purpose, the Flory—Huggins % parameters were also determined from osmotic pressures for some polymer/solvent systems. The Flory—Rehner swelling equation, extended to copolymer networks by Kojima et al., reproduced qualitatively the former two types of swelling behaviour. For the last type, the Flory-Huggins % parameters were obtained from the experimental swelling degrees, from which it was suggested that an inflection point in the curve of swelling degree versus solvent composition appeared in the vicinity of the θ state.

UCST behaviour for high-molecular-weight polymer blends and estimation of segmental χ parameters from their miscibility

Abstract An upper critical solution temperature (UCST) type of miscibility was observed for high-molecular-weight polymer blends of poly(methyl methacrylate) (PMMA) with poly(n-butyl methacrylate) (PnBMA) and with poly(isobutyl methacrylate) (PiBMA). The blends containing random copolymers consisting of these methacrylate monomer units also showed UCST-type miscibility over all copolymer compositions. The segmental interaction parameters χMMA/nBMA, χMMA/iBMA and χiBMA/nBMA were estimated from the dependence of the miscibility on the copolymer composition using the Flory-Huggins theory applied to the random copolymer blends. The temperature dependence of χMMA/nBMA and χMMA/iBMA was required to be comparatively strong in the temperature range above χcrit, while χiBMA/nBMA did not depend so much on the temperature. Quadratic functions of temperature were more appropriate for χMMA/nBMA, χMMA/iBMA and χiBMA/nBMA than another type of function that is proportional to 1/T. The absolute values of all χi/j estimated here were very small compared with those for other immiscible polymer blends. This means that the exchange free energy between the different methacrylate components is very small, which is considered to bring UCST-type miscibility to the high-molecular-weight polymer blends studied here.

A consideration on miscibility behaviour in random copolymer blends based on the equation-of-state theory

Abstract So-called miscibility and immiscibility windows in random copolymer blends are terms that describe the variation in miscibility with copolymer composition, i.e. immiscible → miscible → immiscible and miscible → immiscible → miscible, respectively. The miscibility has been explained by the change of sign of the intermolecular interaction parameter χ expressed in terms of the intersegmental interaction parameters. For the former and the latter windows the sign of the intermolecular parameter χ changes with copolymer composition from positive → negative → positive and negative → positive → negative, respectively. However, the changing pattern of the sign of χ may depend on temperature because the Flory-Huggins interaction parameter χ depends on temperature. Florys equation-of-state theory gives two kinds of temperature dependence of χ: (a) a U-shaped curve, which is always positive, and (b) a function increasing monotonically from negative to positive. In this report we discuss, on the basis of Florys equation-of-state theory, how the pattern of the temperature dependence of χ changes with copolymer composition for copolymer blends. In consequence, even though the sign of χ changes with copolymer composition from positive → negative → positive in a limited temperature range, there were two types of dependences of temperature versus χ curve on copolymer composition: (1) (b) regardless of the copolymer composition as well as (2) (a) → (b) → (a) with copolymer composition predicted by theory. Also, for the blends in which χ changes from negative → positive → negative at a certain temperature, two types were obtained: (3) (b) regardless of the copolymer composition as well as (4) (b) → (a) → (b) with copolymer composition. U-shaped curves can be found only in types (2) and (4); namely in these two types there exists a copolymer composition range where the two polymers are immiscible regardless of temperature. Therefore, it was concluded that so-called miscibility and immiscibility windows should be defined by types (2) and (4), respectively, even though the miscibility change is observed to be immiscible → miscible → immiscible or miscible → immiscible → miscible with copolymer composition in a limited range of temperature.

Thermodynamics of oligomer blends of poly(methylphenylsiloxane) and polystyrene

Abstract Heats of mixing to infinite dilution ΔH M (∞), excess volumes V E and cloud-point curves were experimentally determined for an upper critical solution temperature type of system, the poly(methylphenyl-siloxane)/polystyrene oligomer blend. ΔH M (∞) was positive and V E negative. Florys equation-of-state theory with modified combining rules was applied to this system. The theory with the positive value of the exchange enthalpy parameter reproduced the experimental thermodynamic properties except for the location of the maximum point in the cloud-point curves.

Thermodynamics of poly(dimethylsiloxane) solutions

Improved expressions for thermodynamic excess functions for mixtures of a non-polar polymer and a solvent are presented on the basis of modification of the combining rules of mixing which were assumed by Flory in the equation-of-state theory of pure fluids and their solutions. The modified theory assumes that the number of external degrees of freedom is non-additive with respect to the segment fraction and that the sizes of the core volumes of segments in pure liquids and solution are different. This theory can reproduce the experimental results of the interaction parameter χ and the excess volume of mixing, which the Flory theory failed to reproduce. Direct comparisons of the modified combining rules with experimental results is satisfactory.

Surface free energy of poly(vinyl alcohol) modified with alkyl groups

Abstract The dispersive component of surface free energy γ S d and the nondispersive interactions with polar liquids I SW were determined for poly(vinyl alcohol) (PVA) copolymers having various types of alkyl groups, i.e., four kinds of partly alkyl acetalized PVAs (AIPVA), butyl vinyl ether — vinyl alcohol copolymers (BuVA), ethylene — vinyl alcohol copolymers (EtVA) and BuPVAPVA mixtures. γ S d and I SW were estimated from the measurements of contact angles by means of a two-liquid method proposed by Matsunaga and Ikada. γ S d and I SW for AIPVA, which were smaller than those for PVA itself, decreased with increases in either content or chain-length of the alkyl side group, while γ S d for EtVA was virtually independent of ethylene content. The dependences of γ S d and I SW on the alkyl side chain content per vinyl repeating unit for BuPVA were smaller than those for BuVA. The result for the polymer blends of PVA and BuPVA showed that both γ S d and I SW fell rapidly even at very small addition of BuPVA. The surface free energy γ S (= γ post|staggered|S d + γ S d ) was found to decrease with increasing alkyl group content except for EtVA.

Syntheses of Vinyl Sulfoxide/Vinyl Acetate-Type Copolymers

Abstract The homopolymerization of a series of alkyl vinyl sulfoxides (CH2[dbnd]CHSOR; R = CH3 (MVSO), C2H5 (EVSO), t-C4H9 (BVSO)) and their copolymerization with vinyl acetate (VAc) with 2,2′-azobisisobutyronitrile (AIBN) as initiator at 60°C was attempted. MVSO was found to homopolymerize radically, but EVSO and BVSO were not. Poly-MVSO is soluble in chloroform, methanol, DMSO, and water, but insoluble in acetone and benzene. MVSO and EVSO were found to copolymerize with VAc, but BVSO was not. The copolymerization parameters obtained for both systems were as follows; r1(MVSO) = 2.23, r2 (VAc) = 0.09, and r1(EVSO) = 3.40, r2 (VAc) = 0.11, respectively. MVSO/vinyl alcohol (VA) copolymers were obtained through the saponification of MVSO/VAc copolymers by sodium hydroxide in methanol. The solubility of MVSO/VAc and of MVSO/VA copolymers toward various solvents was examined, and it was observed that the sulfoxide comonomer has a tendency to give amphiphilicit to poly(vinyl acetate) and poly(vinyl alcohol). T...