Kiyokazu Imai

Environmentally induced macromolecular rearrangement on the surface of polyurethane−polysiloxane graft copolymers

Abstract The surface of polyurethane-polysiloxane graft copolymers possessing a controlled polysiloxane graft segment length and a defined siloxane content was studied in both dry and wet states. The top surface of casted graft copolymer film was covered completely with the polysioloxane component in dry state and the thickness of hte top polysiloxane layer range from more than about 100 A to less than about 20 A depending both on the graft segment length and on the total siloxane content. Along with the change of contacting medium from dry to aqueous phase, a dynamic surface rearrangement was observed during a 3-h period from a polysiloxane-like surface to a polyurethane-like surface only when the top polysiloxane layer of graft copolymers in dry state was less than around 100 A.

Surface studies on poly(vinyl alcohol)-poly(dimethylsiloxane) graft copolymers

Abstract The surface structure and properties of poly(vinyl alcohol)-poly(dimethylsiloxane), PVAL-PDMS, graft copolymers with the controlled PDMS graft chain length as well as chain distribution were studied. The surface of the graft copolymer was examined by XPS technique and was found to be covered with essentially pure PDMS graft component even in only 5 mole% siloxane unit content. The contact angle measurement was carried out with the water-in-air technique for PVAL—PDMS graft copolymers as well as the graft copolymer/PVAL homopolymer blends and the significant surface accumulation of PDMS graft component was confirmed with the graft copolymer/PVAL blend of less than 1 mole% of siloxane unit content. In contact with water, PVAL—PDMS graft copolymer surface was found to transform its surface morphology remarkably, which was noticed by the contact angle measurement with the air-in-water technique, where the contact angle of PVAL—PDMS graft copolymer surface was found to differ from that of pure PDMS—coated surface.

Environmentally induced macromolecular rearrangement on the surface of polyurethane–polysiloxane block copolymers

The surface of polyurethane–polysiloxane block copolymers with a controlled polysiloxane block segment length and defined siloxane content has been studied in dry and in wet states. The top surface of a cast block copolymer film was covered completely with the polysiloxane component in the dry state and the thickness of the top polysiloxane layer ranged from > 100 A to < 20 A depending on the block segment length and on the total siloxane content. Along with the change of contacting medium from dry to aqueous phase, a dynamic surface rearrangement occurred from a polysiloxane surface to polyurethane-like surface and the dynamics were monitored by means of contact-angle measurements with a captive bubble technique. The dynamics of this surface rearrangement process were systematically correlated with the total siloxane content and with the polysiloxane segment length. The type of polysiloxane segment, either block or graft, affected the surface dynamics markedly.

Determination of substituent distribution in cellulose ethers by 13C- and 1H-N.M.R. studies of their acetylated derivatives: O-(2-hydroxypropyl)cellulose

Abstract Structural characteristics of O-(2-hydroxypropyl)cellulose samples, namely the molar substitution (mol. subst.), the total degree of substitution (d.s.), and the individual degree of substitution of hydroxyl groups on the glucose residues for a wide mol. subst. range of samples were determined after peracetylation by 1H- and 13C-n.m.r. analyses. The mol. subst. value was determined by comparing the acetyl methyl proton signal with that of the 2-hydroxypropyl methyl group. The acetyl carbonyl carbon signal of acetylated O-(2-hydroxypropyl)cellulose samples was found to split into a quadruplet in Me2SO at 100°, reflecting the position of the substituent (2, 3, and 6) on the glucose residue and of the (oligo-)propylene oxide substituent end-group, and allowing determination of the substituent distribution as well as the total degree of substitution in a series of O-(2-hydroxypropyl)cellulose samples.

Determination of substituent distribution in cellulose ethers by means of a 13C nuclear magnetic resonance study on their acetylated derivatives: 3. Hydroxyethylcellulose

Abstract The distribution of substituent, i.e. oligo(ethylene oxide) groups, in hydroxyethylcelluloses having various values of molar substitution was determined by means of 13 C nuclear magnetic resonance after the acetylation of hydroxyl groups both at the unsubstituted position in the anhydroglucose unit and at the substituent end position of the parent hydroxyethylcellulose. The acetyl carbonyl signal of the acetylated hydroxyethylcellulose samples was found to split into a triplet in DMSO-d 6 at 100°C corresponding to the positions of acetyl groups (2, 3 or 6 overlapped with the substituent end) on the anhydroglucose unit. While in CDCl 3 at 40°C, the acetyl carbonyl signal for the substituent end position was observed to be separated from those on the anhydroglucose unit. By combining these results, the distribution of the substituent groups was determined for a series of hydroxyethylcellulose samples of a wide range of molar substitution values.

Synthesis of polyurethane-polysiloxane graft copolymer using uniform-size poly(dimethylsiloxane) with a diol end group

Abstract A series of uniform-size poly(dimethylsiloxane)s (PDMS) containing a diol end group were synthesized by hydrosilylation of PDMS containing a silane end group with 3-allyloxy-1,2-propanediol. The polyurethane-polysiloxane graft copolymer was then synthesized by two different methods: polyaddition of uniform-size PDMS having a diol end group with 4,4′-diphenylmethanediisocyanate (MDI), followed by chain extension with 1,4-butanediol (BD); and polyaddition of BD and MDI, followed by chain extension with uniform-size PDMS having a diol end group.

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.

Environmental responses on the surface of poly(vinyl alcohol)/poly(tetrahydrofuran) graft copolymers

Abstract The surface of a series of poly(vinyl alcohol)-poly(tetrahydrofuran) graft copolymers possessing controlled graft segment length and graft content was studied by means of contact angle measurements both in water-in-air and in air-in-water techniques. A significant surface rearrangement was observed along with the change of the contacting medium from air to water. Contact angle values in air were almost identical to that of PTHF homopolymer, while in water they were close to that of PVAL homopolymer.

A new bifunctional initiator for the living polymerization of hexamethylcyclotrisiloxane

SummaryA bifunctional living poly(dimethylsiloxane), poly(DMS), was synthesized through the anionic ring-opening polymerization of hexamethylcyclotrisiloxane(D3) (3) with an initiator system consisting of dilithium salt(2) of bis (p-hydroxydimethylsilyl)phenyl ether(1) and N-methylpyrrolidine in THF solution. The subsequent end-capping reaction of the bifunctional living poly(DMS) with dimethylvinylchlorosilane(4) provided the uniform size poly(DMS) having vinylsilane group at the both chain ends(5).