Showing papers by "Virgil Percec published in 1982"

New telechelic polymers and sequential copolymers by polyfunctional initiator-transfer agents (inifers)

Abstract: The possibility of undesirable intramolecular cycloalkylation exists in the polymerization of iso-butylene induced by the p-dicumyl chloride/BCl3 inifer system. A scheme has been proposed which shows the sequence of reactions leading to indane skeletons. The structure of the indane derivatives has been characterized by 1H NMR spectroscopy. Systematic experiments have been carried out using low isobutylene and high p-dicumyl chloride concentrations leading to polyisobutylene oligomers needed for accurate endgroup analysis. The effect of temperature, solvent composition (polar/nonpolar) , isobutylene and BCl3 concentration on the extent of indane skeleton formation has been investigated. Indane skeleton formation can be completely suppressed by the use of relatively non-polar media, e.g., 1∶1 mixture of CH2Cl2 :n-C6H14, at or below −40°C, and conditions under which symmetrical telechelic polyisobutylenes can be obtained have been defined.

New telechelic polymers and sequential copolymers by polyfunctional initiator-transfer agents (Inifers): 28. Glycidyl ethers of bisphenol- and trisphenol-PIB and their curing to epoxy resins

Abstract: SummaryGlycidyl ethers of bisphenol- and trisphenol-polyisobutylenes have been prepared, characterized, and cured with amines to new flexible epoxy resins. The synthesis of these glycidyl ethers involved quantitative condensation of epichlorohydrin with phenol-capped linear or three-arm star polyisobutylenes. Proton NMR analysis of the model compound monoglycidyl ether of 2,4,4-trimethyl-2(p-hydroxyphenyl)pentane and the corresponding glycidyl ethers of phenol-capped polyisobutylenes showed the presence of epoxy end groups. According to 1H NMR spectroscopy and titration data the number-average terminal epoxy functionality is close to the theory, i.e., two or three, for the linear and three-arm star products. Curing these new epoxides with triethylene tetramine resulted in transparent, non-tacky flexible films.

New telechelic polymers and sequential copolymers by polyfunctional initiator-transfer agents (Inifers): 27. Bisphenol- and trisphenol-polyisobutylenes

Abstract: SummaryThe synthesis and quantitative end group characterization of bisphenol- and trisphenol-polyisobutylenes are described. These new telechelic prepolymers consist of a linear or a threearm star polyisobutylene (PIB) carrying exactly two or three phenol termini, respectively. The syntheses were accomplished by quantitative Friedel-Crafts alkylation of phenol by olefin- and/or tert.-chlorine-telechelic PIB's and characterization involved 1H NMR, UV and GPC techniques. These materials combine the chemical versatility of the- C(CH3)2C6H4OH end group with the attractive physical-chemical properties of the rubbery PIB chain.

Donor-acceptor complexation in macromolecular systems

Abstract: Blends of donor-macromolecules — poly(N-(2-hydroxyethyl)-carb-azolyl)methacrylate — with acceptor-macromolecules — poly(methacryloyl-β-hydroxyethyl-3,5-dinitrobenzoate) — exhibit unique dynamic mechanical properties over a broad range of frequency and temperature when compared with those of the components. The complexation between the unlike polymers determines the topology of the thermoreversible network. Plateau modulus is extended into the low frequency and high temperature region dramatically. Corresponding copolymers show up minor improvement of the properties only depending on the donor-acceptor ratio within the macromolecular chain. Thus, the efficacy of intermolecular thermoreversible crosslinking clearly is evidenced.

Intramolecular charge transfer complexes. VIII. Poly[N-(2-hydroxyethyl) carbazolyl acrylate-co-2,4-dinitrophenyl methacrylate]

Abstract: Radical copolymerization of N-(2-hydroxyethyl) carbazolyl acrylate (HECA, M1) with 2,4-dinitrophenyl methacrylate (DNPM, M2) can be described by a simple terminal mechanism having the relative reactivities r1 = 0.14, r2 = 1.10 (at 60°C); 0.28, 0.96 (80°C); and 0.41, 0.79 (100°C), respectively. The dependence of the reactivity ratio values on copolymerization temperature, analyzed by Arrhenius equation, takes place mainly through the frequency factor. The copolymers obtained are intramolecular charge transfer complexes. The intramolecular interaction is evidenced by the shift of the aromatic protons from the DNPM structural unit in the copolymers' 1H-NMR (nuclear magnetic resonance) spectra. This shift depends on sequence distribution and chain conformation, but is not affected by the copolymerization temperature.

New telechelic polymers and sequential copolymers by polyfunctional initiator-transfer agents (Inifers): 25. Synthesis and characterization of ?, ?-di(Allyl) polyisobutylene

Abstract: Summaryα, ω-Di(hydroxy)polyisobutylene was converted to the corresponding α,ω-di(allylether)- and α,ω-di(allylphthalyl)polyisobutylene by reacting the diol with allyl bromide in the presence of alkali and tetrabutylammonium bisulfate phase transfer catalyst, and monoallyl phthalic acid chloride in the presence of 4-N,N-dimethylaminopyridine, respectively. The reaction conditions were defined by suitable model experiments. IR and 1H-NMR analysis of the reaction products indicates quantitative conversions.

New telechelic polymers and sequential copolymers by polyfunctional initiator-transfer agents (INIFERS): 23. Interactions between alcohol-telechelic linear and three-arm star polyisobutylenes and pyromellitic dianhydride

Abstract: SummaryLinear and three-arm star hydroxy-telechelic polyisobutylenes have been quantitatively esterified with pyromellitic dianhydide in the presence of 4-N,N′-dimethylaminopyridine in tetrahydrofuran at room temperature. Chain extension occurred only under reflux conditions (67°C). In the presence of chromium acetyl acetonate catalyst at 140°C insoluble networks were obtained within minutes.