Kazunori Se

Model block–graft copolymer via anionic living polymerization: Preparation and characterization of polystyrene‐block‐[poly(p‐hydroxystyrene)‐graft‐poly(ethylene oxide)]‐block‐polystyrene

A model graft copolymer in which position of graft points was set to the center of a backbone molecule was prepared via anionic living polymerization. Polystyrene-block-poly(p-tert-butoxystyrene)-block-polystyrene (PSt-b-PBSt-b-PSt) was prepared by three-stage sequential addition. The tert-butyl group was removed from PBSt by hydrogen bromide to yield PSt-b-PHSt-b-PSt, having a poly(p-hydroxystyrene) (PHSt) block. The hydroxyl group of PHSt was reacted with dimeric potassium dianions of 1, 1-diphenylethylene (DPE-K) or cumyl potassium (cumyl K) to yield the corresponding macromolecular initiators of PSt-b-PHSt−K+-b-PSt containing the potassium alkoxide ion of PHSt. The newly formed alkoxide groups and remaining initiators of DPE-K or cumyl K are capable of initiating the additionally introduced ethylene oxide (EO). Thus, two block–graft copolymers of polystyrene-block-[poly(p-hydroxystyrene)-graft-poly(ethylene oxide)]-block-polystyrene (PSt-b-(PHSt-g-PEO)-b-PSt) were prepared by a “grafting from” process (backbone initiation). A PSt-b-PHSt-b-PSt backbone (Mn = 1.75 × 105 by osmometry and Mw/Mn = 1.08 by GPC), and two PSt-b-(PHSt-g-PEO)-b-PSt block–graft copolymers (Mn = 2.45 × 105 by osmometry and Mw/Mn < 1.10 by GPC) had narrow molecular weight distributions. A relationship between nonquantitative metallation and spacing of the graft points on a backbone molecule was discussed in detail. Two benzene-cast films formed clear microphase-separated structures of lamellar structure. The dependence of composition on the morphology of the block–graft copolymers was found to differ from that of common block copolymers. A degree of crystallinity of PEO segment and lamellar thickness of PEO phase serving as graft molecule were also found to differ from those of homo PEO and/or PEO segment in common block copolymer.

Molecular weight determination of star polymers and star block copolymers using GPC equipped with low-angle laser light-scattering

Abstract Gel permeation chromatography equipped with a low-angle laser light-scattering detector (GPC-LALLS) was employed to determine the M n and M w of any polymer system such as flexible polymers (polystyrene, PSt), rod-like polymers (poly( n -hexylisocyanate), PIC), star polymers ((PSt) n and [poly(α-methylstyrene)] 4 , (PαMSt) 4 ), linear block copolymers (polystyrene- block -polyisoprene, PSt- block -PIs) and star block copolymers ((PSt) 4 - star -(PIs) 7 ). For the homopolymers (PSt, PIC, (PSt) n and (PαMSt) 4 ), the determined M n GPC-LS and M w GPC-LS values are in good agreement with the M n OSM and M w LS values determined by osmometry and light scattering, respectively. For the block copolymers (PSt- block -PIs and (PSt) 4 - star -(PIs) 7 ), two composition distributions (CDs) have to be considered: one is a CD among the different molecular weights and the other is a CD among the same molecular weights. Block copolymers are classified into four groups from the viewpoint of a combination of the two CDs. In any group, new analytical equations for determining M n and M w were derived by the assumption that the block copolymers, which appear at the same elution volume of the GPC chromatogram, have the same molecular weights. The resultant M n BC GPC - LS values were in good agreement with the M n OSM values. GPC-LALLS was found available for determining M n and M w of the block copolymers.

Photochemical isomerization of azobenzene incorporated in poly(N,N-dimethyl-4-vinylphenethylamine-block-styrene) diblock copolymer by cross linkage

Abstract Photochemical isomerization of p,p′-bis(chloromethyl) azobenzene (CAB) was investigated in poly-(N,N-dimethyl-4-vinylphenethylamine-block-styrene) block copolymer [P(PTA-b-St)]. The P(PTA-b-St) was prepared by anionic living polymerization. Both ends of CAB were attached to amino groups of the PPTA in the P(PTA-b-St) by quaternization in order to permit cross-linked films. When the films were irradiated with u.v. light (300 nm

Quaternization of poly(tertiary aminostyrene)s and characterization of the quaternized polymers

The Menschutkin reaction of three poly( tertiary aminostyrene)s: poly(N,-N-dimethyl-4-vinylphenylamine) (PPA), poly(N,N-dimethyl-4-vinylbenzylamine) (ABA), and poly(N,N-dimethyl-4-vinylphenethylamine) (PPTA) was investigated. These three polymers having narrow molecular weight distributions were prepared via anionic living polymerization. PPA reacted homogeneously with n-butyl bromide in N,N-di-methylformamide (DMF). PBA and PPTA also reacted homogeneously with n-butyl bromide in a mixture of DMF/methanol (75/25 v/v %). GPC measurement of the quaternized polymers was carried out using a mixture of water/acetonitrile (80/20 v/ v %) containing 0.5M acetic acid and 0.3M sodium sulfate (pH = 2.9 ) as an eluant in order to suppress adsorption of the quaternized water soluble polymers on GPC gel. Results of GPC measurement indicate that the polymer chains of the three poly ( tertiary aminostyrene)s are neither severed nor crosslinked in the process of quaternization. Temperature dependence and reaction time dependence on the degree of quaternization ( DQ ) were studied for PPT, PBA, and PPTA. By altering reaction time and temperature, the DQ values of the three poly(tertiary aminostyrene)s could be controlled in the range from 0% to nearly 100%. Quaternization reactivity of the amino groups in the three polymers was found to decrease in the order, PPTA, PBA, and PPA. The differences in reactivity are thought to be attributable to the electron density on the nitrogen atom of the N,N-dimethylamino group, and steric hindrance in the vicinity of the nitrogen atom.

Grafting of oligopeptide on poly(aminostyrene)s and characterization of the polymers

Graft copolymers that have oligopeptides (OP) as graft molecules were prepared through the coupling reaction of the carboxylic acids of OP with the amino groups of poly(aminostyrene)s (PAS). The three OPs are Boc-Gly, Z-Gly-Pro, and Z-Gly-Pro-Leu-Gly-Pro, where Boc and Z are, respectively, the t-butyloxycarbonyl group and benzyloxycarbonyl group as protective groups on nitrogen. The two PASs are poly(4-vinylphenylamine) and poly(N-isopropyl-4-vinylbenzylamine). These polymers that have narrow molecular weight distributions were prepared via anionic living polymerization. The coupling reaction to form the peptide bonds was mediated by dicyclohexylcarbodiimide in a mixed solvent of N,N′-dimethylformamide and methyl chloride. The degree of grafting (DOG) on PAS was determined from the 1H-NMR spectrum. The dependence of the reaction time (0–8 h) on the DOG, the dependence of the reaction temperature (0–45°C) on the DOG, and the dependence of the molar ratio of OP to the amino group of PAS (1–4 times) on the DOG were studied. By alternating the reaction time and the molar ratio, the DOG values of PAS could be controlled in the range from 0 to 100%. DOG seems to be independent of the molecular weight of OP and the degree of basicity of PAS. The contact angle of the resultant graft copolymers was measured and the preliminary nonthrombogenic test was also performed.

Electrical properties of urethane-substituted polydiacetylene

Abstract Conjugated backbones of p-3BCMU were modified either by UV-irradiation, accompanying chain scission and Cl addition, or bromination in CHCl 3 solutions. As the content of Cl and Br in p-3BCMU increased, conductivity decreased, and the activation energy increased. These results could be explained by the average length of effective conjugation, which was calculated by the content of halogen and the molecular weight by assuming that the halogenated sites and the chain ends act as defects.