ISSN:0360-8905    

DOI:10.1002/polc.5070450103

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1974

数据来源: WILEY

摘要:

AbstractCooperative and electrostatic effects were investigated for the hydrolysis of charged and neutral substrates catalyzed by a copolymer containing pendant nucleophiles (imidazole groups) and permanent positive charges (quaternary imidazolium halides). Limited evidence was also presented for apolar bonding in the hydrolysis of long chain anionic substrates catalyzed by a copolymer of 4 (5)‐vinylimidazole and 2, 3‐dimethyl‐1‐vinylimidazolium iodide (plm +

ISSN:0360-8905    

DOI:10.1002/polc.5070450104

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1974

数据来源: WILEY

摘要:

AbstractIn this work are discussed the reactions of 2‐vinylpyridine and 2‐methyl‐5‐vinylpyridine with dilute and concentrated acid solutions. In reactions with dilute acid, the concept of pyridyl‐ethylation leading to initiation of polymerization was studied for both monomers. Although this reaction was applicable for 2‐vinylpyridinium salts, it apparently did not occur with 2‐methyl‐5‐vinylpyridinium salts. In reactions with concentrated acid, both monomers have been found to polymerize spontaneously to high molecular weight polymers. In addition, an analysis of the neutralized polymers by gel permeation chromatography (GPC) has shown them to be of narrow molecular weight distribution. An investigation of the effect of air or oxygen on these reactions has shown that they do not significantly alter the resulting molecular weights or molecular weight distributions that can be obtained. From a study of the percent conversion versus time, the data obtained indicated that these spontaneous polymerization reactions are chain

ISSN:0360-8905    

DOI:10.1002/polc.5070450105

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1974

数据来源: WILEY

摘要:

AbstractThe homopolymerizations of a series of 3‐n‐alkyl‐1‐vinylimidazolium iodides are described in which the length of the quaternizing alkyl group was varied from methyl to n‐propyl to n‐hexyl to n‐heptyl to n‐dodecyl to n‐hexadecyl. The preparations of these cationic monomers have previously been reported through reaction of 1‐vinylimidazole with the corresponding n‐alkyl iodide. All polymerizations were performed in aqueous solution at the same molar concentration of monomer using the free radical initiator 4,4′‐azobis‐4‐cyanopentanoic acid. It was found that the short side‐chain polyions (methyl and n‐propyl) were water soluble, whereas the more hydrophobic intermediate side‐chain polyions (n‐hexyl and n‐heptyl) were water insoluble. The long side‐chain polyions (n‐dodecyl and n‐hexadecyl), on the other hand, being highly hydrophobic, appeared to form polysoaps and remained in aqueous solution. The solution behavior of these polyions in water, in aqueous salt solution, and in chloroform is discussed as well as is the critical micelle concentration of a long sid

ISSN:0360-8905    

DOI:10.1002/polc.5070450106

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1974

数据来源: WILEY

摘要:

AbstractMany important naturally occurring biochemical reactions such as synthesis of nucleic acids, proteins, and polysaccharides proceed through template polymerization. Such reactions are very complex, and the study of simpler systems is of great interest.A radical initiated polymerization of p‐styrene sulfonic acid anion attached to a poly(quaternary ammonium) backbone (ionene) was studied. The polycationic matrix was prepared from 1–4 diazobi‐cyclo (2.2.2.) octane and 1–4 dibromobutane. It was of low molecular weight (5–10 monomeric units), high rigidity, and could be considered to be in a rod‐like conformation in dilute water solutions. The polymerization of the pSSA‐ionene complex was followed by means of ultraviolet spectroscopy. The overall polymerization kinetics was studied as a function of temperature, concentrations of monomer and initiator, and of the “degree of filling” of the matrix at neutral pH. A rate increase of over two orders of magnitude was observed in the presence of the matrix. This effect was maximum for stoichiometric amounts of monomer and matrix and fell off rapidly for lower monomer‐to‐matrix ratios. The kinetic effect is accompanied by a large decrease in the overall activation

ISSN:0360-8905    

DOI:10.1002/polc.5070450107

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1974

数据来源: WILEY

摘要:

AbstractStarch was preirradiated with cobalt‐60 and then allowed to react with mixtures of acrylamide and N,N,N‐trimethylaminoethyl methacrylate methyl sulfate (TMAEMA·MS) in a water solution. The graft copolymers resulting were purified and characterized, and the influence of a number of irradiation and reaction variables on graft copolymer composition was determined. Although the reaction of irradiated starch with monomers must be carried out with a monomer solution purged with nitrogen to remove dissolved oxygen, a nitrogen atmosphere over the starch sample during irradiation is not necessary to achieve graft polymerization. With monomer mixtures containing 2, 5, 10, 15, and 50 mol% TMAEMA·MS, the mole percentage of TMAEMA·MS in grafted branches was less than that in the initial monomer mixture, whereas ungrafted polymer generally contained a higher percentage of the cationic monomer than was present initially. A tenfold variation in irradiation dose (0.5–5.0 Mrad) caused only small variations in percent add‐on; however, intrinsic viscosities of grafted branches decreased with increasing irradiation dose. Substituting aqueous ethylene glycol for water as the reaction medium produced more frequent grafts of lower molecular weight. Graft polymerization onto partially degraded starches gave graft copolymers with better water

ISSN:0360-8905    

DOI:10.1002/polc.5070450108

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1974

数据来源: WILEY

摘要:

AbstractA comparative review of properties of ionomers is presented, stressing primarily the similarities and contrasts between ethylene and styrene based materials. In particular, it is shown, that in the concentration region where ion clustering is encountered, the mechanical properties of the two ionomers resemble each other more closely than do those of the styrene ionomers and styrene. The similarity can be seen from a range of experimental results, and several different approaches are described.

ISSN:0360-8905    

DOI:10.1002/polc.5070450109

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1974

数据来源: WILEY

摘要:

AbstractThe nature of the distribution of ionic groups in cesium salts of ethylene‐methacrylic acid and ethylene‐acrylic acid copolymers containing 2.1 to 6.3 mol% acid was examined using the small‐angle and wide‐angle x‐ray scattering techniques. The low‐angle data containing a maximum characteristic of these materials were analyzed according to principles of small‐angle scattering theory. The radial distribution functions for a typical salt and unionized copolymer were derived from the combined small‐ and wide‐angle data. The results of these two approaches indicate the presence of ionic clusters of the order of 10–20 Å in size. There is evidence that these clusters are of spherical geometry. The low‐angle maximum is interpreted as an interference resulting from short range ordering of ionic groups

ISSN:0360-8905    

DOI:10.1002/polc.5070450110

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1974

数据来源: WILEY

摘要:

AbstractStyrene/n‐butyl methacrylate/potassium methacrylate ionomers have been prepared by partial alkaline hydrolysis of the copolymers. Ion contents were determined by atomic absorption and neutron activation analyses. Glass transition temperatures (by DSC) increase with ion content but reach limiting values at 1–2 mol % ions. The limiting values are 5–20° higher than those of the starting polymers—depending on the molecular weight–and increase linearly with styrene content. These relationships are approximately described by Tg= Tgx ‐ (K/M + 4)e−xwhere x is the molar ion content, Tg∞ is the limiting Tgvalue and M the molecular weight. Data are provided to indicate that the Tgincrease due to introduction of ions can be balanced by aqueous plasticization at ambient relative humidity, but the sharp shoulders in the Tgvariations suggest the presence of a more fundamental mechanism in addition to this. Onset of domain formation or transition from growth of number of domains to growth of the size of these domains are possible mechanisms. Hydrolysis of polyacrylates can be accompanied by intramolecular catalysis leading to less random distribution of ions in the chains. Comparative studies were made with an alternating styrene/n‐butyl methacrylate copolymer in which this effect cannot occur. Hydrolysis rate was comparable to that of the random copolymers suggesting the absence of this effect under our conditions. Ionomers prepared from the alternating copolymer showed the characteristic Tgshoulder, indicating that this is not a consequence of b

ISSN:0360-8905    

DOI:10.1002/polc.5070450111

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1974

数据来源: WILEY

摘要:

AbstractThis study concerns the ion containing terpolymers of styrene, n‐butylmethacrylate, and potassium methacrylate (S/n‐BMA/K+MA−) produced by the partial hydrolysis of random S/n‐BMA copolymers. The extent of hydrolysis resulted in terpolymers having 1 to 5 mol % potassium ions. The introduction of ionic sites produces labile crosslinks in these low‐molecular weight amorphous polymers which are reflected in many of the physical properties. The effects of temperature, shear rate, and shear stress on steady state and dynamic rheological properties are examined as functions of molecular parameters (ion content, S/n‐BMA composition, and molecular weight). The dependence of viscosity on composition and molecular weight are complicated by the occurrence of molecular entanglements at lower molecular weights as the proportion of n‐BMA is increased. It is found that the Newtonian viscosity, at constant T‐Tg, varies exponentially with the molar ion content. The rate of log viscosity increase with molar ion content varies as the inverse molecular weight of the S/n‐BMA copolymers in the region of molecular weights studied. At ion contents above about 4 mol % potassium ions, the system is rheologically complex. The viscosity exhibits different shear dependence in steady state and in oscillatory response, and the temperature dependence of the shift factor log aTchanges abruptly. These have generally been taken to indicate some degree of ion clustering, although no direct evidence for the existence of clusters by low angle x‐ray studies has so far been observed

ISSN:0360-8905    

DOI:10.1002/polc.5070450112

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1974

数据来源: WILEY