摘要:

AbstractThree acrylic monomers bearing 4′‐dialkylamino‐4‐nitro‐stilbene and ‐azobenzene dyes have been synthesized. The monomeric dyes were homopolymerized and copolymerized with methyl methacrylate using a free radical initiator to produce polymers useful for nonlinear optics. Comparison of the solubility and molecular weight distribution data between stilbene‐ and azobenzene‐containing polymers indicated that some crosslinking occurred during polymerization with the stilbene monomers, presumably through the internal double bond in the dye. The dye‐containing homopolymers exhibit liquid crystallinity. Some interaction among the pendant dyes was detected by vis

ISSN:0887-624X    

DOI:10.1002/pola.1990.080280101

出版商:John Wiley&Sons, Inc.    

年代:1990

数据来源: WILEY

摘要:

AbstractThe ethylene polymerization by Cp2ZrCl2/MAO (Cp = η5: cyclopentadienyl; MAO = methyl aluminoxane) and CpZrCl3/MAO have been studied. The MW and PD (=Mw/Mw) of polymers obtained after 2.5‐60 min are the same, which indicate short chain lifetime. The values of rate constants for Cp2ZrCl2at 70°C are:kp= 168−1670 (Ms)−1andktrA1= 0.012‐0.81 s−1depending upon [Zr] and [MAO,]ktrβ= 0.28 s−1, andktrH= 0.2M−1torr−1/2s−1. These chain transfer rate constant values are two to three orders of magnitude greater than the corresponding values found for MgCl2supported titanium catalysts. One significant difference between the heterogeneous and homogeneous catalysts is that the former decays according to an apparent second order kinetics, whereas the latter decay is simple first order at 0°C and biphasic first order at higher temperatures. The productivity of the catalysts depends weekly on temperature while the MW decreases strongly with increase of temperature above 30°C. All the active species were formed upon mixing Cp2ZrCl2with MAO while it took up to 20 min for the CpZnCl3/MAO system. The productivity of the former increase more strongly with the decrease of [Zr] than the latter. Otherwise, the two catalyst systems have all their kinetic parameters differing les

ISSN:0887-624X    

DOI:10.1002/pola.1990.080280102

出版商:John Wiley&Sons, Inc.    

年代:1990

数据来源: WILEY

摘要:

AbstractA statistical model for network formation by the free‐radical copolymerization and crosslinking reaction with small crosslinker content is used to obtain expressions for structural averages as a function of reaction parameters. The analysis accounts for reaction features that are characteristic of free‐radical mechanisms and can be adapted to include cyclization, various modes of termination, and the gel effect. Profiles for structural averages such as the weight average molecular weight, the sol weight fraction, the molecular weight between crosslinks, and the number of elastically active network chains are obtained as functions of convers

ISSN:0887-624X    

DOI:10.1002/pola.1990.080280103

出版商:John Wiley&Sons, Inc.    

年代:1990

数据来源: WILEY

摘要:

AbstractMercapto‐16‐crown‐5 was prepared starting from tetraethyleneglycol and 3‐chloro‐2‐chloromethyl‐1‐propene. Radical polymerization of methyl methacrylate was carried out in the presence of mercapto‐16‐crown‐5 as a chain transfer agent to give crown ether‐terminated poly(methyl methacrylate). The end crown group was characterized by IR and1H‐NMR spectra. Sodium cation was selectively extracted by this crown‐containing polymer. The molecular weight of the obtained polymer had influence upon the ability of

ISSN:0887-624X    

DOI:10.1002/pola.1990.080280104

出版商:John Wiley&Sons, Inc.    

年代:1990

数据来源: WILEY

摘要:

AbstractPoly(L‐ornithine) having azo aromatic side chain was synthesized by the water‐soluble carbodiimide procedure. The photochemical properties of the azo polypeptide poly[Nδ‐p‐(phenylazo)benzoyl‐L‐ornithine] (PPABLO) was investigated by absorption and circular dichroism spectroscopy in hexafluoro‐2‐propanol (HFIP). The photochromism of the dichroic bands in the visible and ultraviolet wavelength regions was found to be reversible as a function of irradiation time at different wavelengths due to the photostationary state (about 70% trans)–cis photoisomerization of the azo aromatic moieties. The reversible photoinduced solubility change was also studied. On irradiation PPABLO is soluble under ultraviolet light (cis) and precipitate under visible light (70% trans) in HFIP–water. A discussion was presented that includes results on azo aro

ISSN:0887-624X    

DOI:10.1002/pola.1990.080280105

出版商:John Wiley&Sons, Inc.    

年代:1990

数据来源: WILEY

摘要:

AbstractWholly aromatic liquid crystalline main chain polyesters derived from terephthalic acid, phenyl‐ or (1‐phenylethyl)hydroquinone modified with either 3,4′‐ or 4,4′‐dicarboxydiphenylether andp‐hydroxybenzoic acid, have been prepared by acidolysis and thermally investigated. All prepared polyesters exhibit excellent thermal stability up to about 400°C, however, the (1‐phenylethyl)hydroquinone polyesters generally showed lower stability. Melting points could be decreased to around 200°C without any decrease in the thermal stability or

ISSN:0887-624X    

DOI:10.1002/pola.1990.080280106

出版商:John Wiley&Sons, Inc.    

年代:1990

数据来源: WILEY

摘要:

AbstractMono‐ and di‐ended linear and three‐arm star allyl‐telechelic polyisobutylenes, PIBA, APIBA and (where A = CH2CHCH2) have been prepared by a rapid economical one‐pot polymerization‐functionalization process. The process involves the living polymerization of isobutylene (IB) by mono‐, di‐, or tri‐functional initiating systems, specifically by allphatic and aromatictert‐ester and ‐ether/TiCl4combinations, followed by electrophilic functionalization of the living sites with allyl‐trimethylsilane (ATMS). Structural characterization by1H‐NMR spectroscopy and end group titration withm‐chloroperbenzoic acid (m‐CPBA) indicate quantitative end allylation even with relatively slowly initiating systems like DiOAcTMH7/TiCl4. Detailed kinetic analysis of the latter system indicates, unexpetedly, cationation to be rate determining. Quantitative derivatizations of the allyl termini have yielded mono‐, di‐, and tri‐epoxy‐ and ‐hydroxy‐telechelic PIBs. Strong rubbery networks have been made by curing the epoxy‐telechelic PIBs with triethylene tetrami

ISSN:0887-624X    

DOI:10.1002/pola.1990.080280107

出版商:John Wiley&Sons, Inc.    

年代:1990

数据来源: WILEY

摘要:

AbstractPoly[4‐(4‐nitrobenzyloxy)styrene] was synthesized with a high degree of etherification by the reaction of poly(4‐hydroxystyrene) (PHST) withp‐bromomethylnitrobenzene (p‐BMNB) using 1,8‐diazabicyclo‐[5,4,0]‐7‐undecene (DBU) in hexamethylphosphoramide (HMPA). Poly[4‐(3‐nitrobenzyloxy)styrene]and poly[4‐(2‐nitrobenzyloxy)styrene] were also prepared with a high degree of etherification by the corresponding reaction withm‐ oro‐BMNBs. However, the degrees of etherification of PHST with these BMNBs were relatively low when the reactions were carried out in other aprotic polar solvents such as DMF, DMSO, andN‐methyl‐2‐pyrrolidone. On the other hand, poly(4‐introbenzyl methacrylate) (PPNBMA), poly(3‐nitrobenzyl methacrylate) (PMNBMA), and poly(2‐nitrobenzyl methacrylate) (PONBMA) were synthesized with a high degree of esterification by the reaction of poly(methacrylic acid) with the corresponding BMNBs using DBU in DMSO at 30°C. The photochemical properties of the resulting poly(nitrobenzyl methacrylate)s were examined, and it was found that the rates of photodecomposition of PPNBMA and PMNBMA were promoted by the addition of tributylamine and trifluoromethanesulfonic acid, respectively. However, the rate of photodecomposition of PONBMA was not af

ISSN:0887-624X    

DOI:10.1002/pola.1990.080280108

出版商:John Wiley&Sons, Inc.    

年代:1990

数据来源: WILEY

摘要:

AbstractSoapless emulsion copolymerization of styrene (S) andn‐butyl acrylate (BuA) has been investigated using two types of initiator and different comonomer feed mixtures. When using K2S2O8as initiator, the particle size and size distribution of the final latexes (500 nm and 1.003, respectively) is not significantly affected by the comonomer feed composition, whereas the molecular weight and surface characteristics were found to sharply change at high butyl acrylate content. Based on the most probable particle nucleation mechanism and type of chain termination in the monomer swollen particles, a tentative explanation of these results has been proposed. Replacing persulfate by a carboxylic initiator (4‐4′‐azobiscyanopentanoic acid) results in the formation of stable particles as α observed with the persulfate, provided the aqueous phase pH is fixed in between 6 and 7. Results on the initiator residue location as a function of the conversion point out that the particle flocculation mechanism is strongly significant in the preparation of such

ISSN:0887-624X    

DOI:10.1002/pola.1990.080280109

出版商:John Wiley&Sons, Inc.    

年代:1990

数据来源: WILEY

摘要:

AbstractEmulsion terpolymerization of styrene (S), butylacrylate (BuA) and sodium acrylamido undecanoate (AUNa), a surface active functional monomer have been carried out using a batch process in the presence of sodium 4‐4′‐azobiscyanopentanoate as initiator. Varying the AUNa concentration, stable particles bearing only carboxylic charges have been produced with diameters ranging from 200 to 500 nm at solids content as high as 40%. However a low AUNa yield at the particle surface has been found (30–35%), which could be explained by very unfavorable reactivity ratios of AUNa with S and BuA. Most of the AUNa seems to be wasted in the water phase (unpolymerized and forming hydrosoluble chains). Furthermore, a concentration of AUNa higher than 10−2mol L−1results in the latex destabilization, presumably caused by the formation of a large amount of polyelectrolytes. Kinetic studies of the AUNa consumption show that the AUNa is mainly fixed at the particle surface between 90 and 100% conversion, which indicates that the AUNa is mainly polymerized in the water phase and not at the particle surface. An attempt has been made to increase the surface charge density by polymerizing a shell of AUNa/S/BuA on a seed latex. It turned out to be unsuccessful (low surface yield, formation of new

ISSN:0887-624X    

DOI:10.1002/pola.1990.080280110

出版商:John Wiley&Sons, Inc.    

年代:1990

数据来源: WILEY