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Living carbocationic polymerization. IV. Living polymerization of isobutyleneThis paper is dedicated to M. Szwarc to commemorate the 30th anniversary of the discovery of anionic “living” polymerizations. (1996)

Faust, R. ; Kennedy, J. P.

Bognor Regis [u.a.] : Wiley-Blackwell

Journal of Polymer Science Part A: Polymer Chemistry 34 (1996), S. 1847-1869

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ISSN: 0887-624X

Keywords: Chemistry ; Polymer and Materials Science

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: Truly living polymerization of isobutylene (IB) has been achieved for the first time by the use of new initiating systems comprising organic acetate-BCl3 complexes under conventional laboratory conditions in various solvents from -10 to -50°C. The overall rates of polymerization are very high, which necessitated the development of the incremental monomer addition (IMA) technique to demonstrate living systems. The living nature of the polymerizations was demonstrated by linear $\[\bar M_n \]$ versus grams polyisobutylene (PIB) formed plots starting at the origin and horizontal number of polymer molecules formed versus amount of polymer formed plots. $\[\overline {DP_n } \]$ obeys [IB]/[CH3COORt · BCl3]. Molecular weight distributions (MWD) are very narrow in homogeneous systems $\[\left( {{{\bar M_w } \mathord{\left/ {\vphantom {{\bar M_w } {\bar M_n = 1.2 - 1.3}}} \right. \kern-\nulldelimiterspace} {\bar M_n = 1.2 - 1.3}}} \right)\]$ whereas somewhat broader values are obtained when the polymer precipitates out of solution $\[\left( {{{\bar M_w } \mathord{\left/ {\vphantom {{\bar M_w } {\bar M_n = 1.4 - 3.0}}} \right. \kern-\nulldelimiterspace} {\bar M_n = 1.4 - 3.0}}} \right)\]$. The MWDs tend to narrow with increasing molecular weights, i.e., with the accumulation of precipitated polymer in the reactor. Traces of moisture do not affect the outcome of living polymerizations. In the presence of monomer both first and second order chain transfer to monomer are avoided even at -10°C. The diagnosis of first and second order chain transfer has been accomplished, and the first order process seems to dominate. Forced termination can be effected either by thermally decomposing the propagating complexes or by nucleophiles. In either case the end groups will be tertiary chlorides. The living polymerization of isobutylene initiated by ester · BCl3 complexes most likely proceeds by a two-component group transfer polymerization.

Additional Material: 8 Ill.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/pola.1996.878

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Living carbocationic copolymerizations. I. Synthesis and characterization of isobutylene/p-methylstyrene copolymers (1995)

Országh, I. ; Nagy, A. ; Kennedy, J. P.

Chichester : Wiley-Blackwell

Journal of Physical Organic Chemistry 8 (1995), S. 258-272

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ISSN: 0894-3230

Keywords: Organic Chemistry ; Physical Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology , Physics

Notes: The isobutylene (IB)-p-methylstyrene (pMeSt) monomer pair readily produces by living copolymerization nearly random copolymers with up to M̄n ≈ 50,000 g mol-1 and M̄w/M̄n ≈ 1·4. The livingness of the copolymerization process and the compositional homogeneity of the copolymers have been demonstrated by the following four diagnostic plots: (A) M̄n (number-average molecular weight) and corresponding N (number of moles of copolymer formed) vs Wp (weight of copolymer formed) for the diagnosis of chaintransfer; (B) -ln (1 - C) (C = conversion of monomers) vs time for the diagnosis of termination; (C) copolymer composition vs molecular weight; and (D) cumulative copolymer composition vs conversion for the diagnosis of true homogeneous copolymers. The theory for the use of the -ln(1 - C) vs time plot for the quantitation of irreversible termination in copolymerization has been developed. The exact conditions (i.e. nature of reagents, reagent concentrations, temperature, etc.) which lead to desirable products in terms of conversion, molecular weight, molecular weight distribution (MWD) and copolymer composition, were developed systematically by analyzing the results of a large number of experiments. The following combination of chemicals was found to lead to living copolymerization, and uniform high molecular weight, narrow MWD copolymers: IB-pMeSt 97 : 3 mol/mol with 5-tert-butyl-1,3-dicumyl methyl ether (5-tBu-1,3-DiCumOMe) initiator, TiCl4 coinitiator, ethyl chloride (EtCl) solvent, triethylamine (TEA) electron pair donor (ED) and 2,6-di-tert-butylpyridine (DtBP) proton trap at -52, -65 and -85°C.

Additional Material: 13 Ill.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/poc.610080409

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Living carbocationic copolymerizations. II. Reactivity ratios and microstructure of isobutylene/p-methylstyrene copolymers (1995)

Nagy, A. ; Országh, I. ; Kennedy, J. P.

Chichester : Wiley-Blackwell

Journal of Physical Organic Chemistry 8 (1995), S. 273-281

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ISSN: 0894-3230

Keywords: Organic Chemistry ; Physical Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology , Physics

Notes: A novel method was developed for the quantitative description of copolymerization behavior, specifically for the derivation of reactivity ratios and micro- and macro-compositions of monomer pairs with significantly different reactivities. The novelty of the method lies in the manner of generating instantaneous feed and copolymer composition data from experimentally readily obtainable cumulative copolymer compositions, although the latter drifts with progressing copolymerization. It is demonstrated that such copolymer systems can be described by two reactivity ratios, albeit the values are valid only over the narrow feed composition range within which they were determined. The great advantage of this method is that whereas the differential copolymer composition equation is strictly valid only at 0% conversion, the method produces corresponding instantaneous feed and copolymer compositions at any conversion. Assumptions or approximations are unnecessary to calculate reactivity ratios. Subsequently the procedure was applied to obtain reliable monomer reactivity ratios of isobutylene (IB)-p-methylstyrene (pMeSt) copolymers, rIB and rpMest, prepared by living carbocationic copolymerizations with [IB]/[pMeSt] feeds compositions of 90:10 and 97:3 mol/mol, i.e., with feed compositions of industrial importance. According to our procedure, rIB = 0·74±0·11 and rpMeSt = 7·99±3·34. These reactivity ratios were then used to calculate overall IB-pMeSt copolymer compositions over the entire comonomer conversion range and to compare calculated with experimental compositions. The good quantitative agreement between calculated and experimental compositions indicates that the description of both macro- and micro-compositions of IB-pMeSt copolymers obtained in the 90:10 and to 97:3 mol/mol feed composition range is satisfactory.

Additional Material: 13 Ill.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/poc.610080410

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Amphiphilic networks. X. Diffusion of glucose and insulin (and nondiffusion of albumin) through amphiphilic membranes (1997)

Shamlou, S. ; Kennedy, J. P. ; Levy, R. P.

Hoboken, NJ : Wiley-Blackwell

Journal of Biomedical Materials Research 35 (1997), S. 157-163

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ISSN: 0021-9304

Keywords: Chemistry ; Polymer and Materials Science

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Medicine , Technology

Notes: Select semipermeable amphiphilic membranes have been prepared and their diffusional characteristics for glucose, insulin, and albumin investigated. The membranes were prepared by cast copolymerization of a hydrophilic monomer (i.e., N,N-dimethyl acrylamide, or N,N-dimethylaminoethyl methacrylate) with the hydrophobic crosslinker methacrylate-ditelechelic polyisobutylene. The products have sufficient mechanical properties for the fabrication of swollen membranes, sheets, tubes, etc. Membranes have been identified which allowed the rapid simultaneous countercurrent diffusion of glucose (Mn = 180 Da) and insulin (Mn = 5733 Da) but did not allow albumin (Mn ∼ 60,000 Da) to pass. Evidently, the effective molecular weight cutoff point of these membranes is in the 6-60-KDa range. © 1997 John Wiley & Sons, Inc.

Additional Material: 3 Ill.

Type of Medium: Electronic Resource

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