摘要:

AbstractThe pH dependence of the interaction of poly(2‐dimethylaminoethyl methacrylate) and copolymers of 2‐dimethylaminoethyl methacrylate andN‐vinyl‐2‐pyrrolidone with methyl orange, 2‐p‐toluidinylnaphthalene‐6‐sulfonate (TNS), and 1,6‐diphenyl‐1,3,5‐hexatriene (DHT) was studied by equilibrium dialysis and fluorescence measurements at pH's 7–10. The first binding constant accompanying the binding of methyl orange and TNS by the polymers, in particular the homopolymer, shows a maximum around pH 8 and maximal fluorescence intensity of TNS is obtained around pH 8.5 in the presence of the polymers. To elucidate these observations the pH‐induced conformational changes of the homopolymer were examined by potentiometric titration and viscosity measurements and the thermodynamic parameters that accompany the binding were calculated. The polymer was found to change from an extended coil at lower pH to a compact coil at higher pH. The electrostatic attraction between the sulfonate group of the small molecule and the protonated nitrogen atoms on the polymer is increased at lower pH and the hydrophobic interaction between the hydrophobic moieties of the polymer and the small molecule is enhanced at higher pH. The results obtained for the dye binding and fluorescence intensity were discussed in terms of the electrostatic a

ISSN:0887-624X    

DOI:10.1002/pola.1989.080270101

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractA spectral method for determining the imidization from maleamic acid to maleimide was described. The formation condition and mechanism of polymaleimide compared withN‐phenyl‐maleimide (I) and 4,4′‐bis(N‐maleimido)‐diphenylmethane (II) were investigated. A series ofN‐substituted maleimides were synthesized by the reaction of their corresponding maleamic acids with acetic anhydride and sodium acetate as a catalyst. The rate of dehydration reaction ofN‐phenylmaleamic acid with Ac2O was determined at a mole ratio 0.1:1 of NaOAc toN‐phenyl‐maleamic acid and a second‐order constantKof 1.38 × 10−2(mL/mol s) was obtained. The activation energies for the ring‐closure reaction ofN‐phenylmaleamic acid and polyphenylene‐methylenemaleamic acid were 1.26 × 104(cal/g mol) and 1.32 × 104(cal/g mol), respectively. The decreasing order for the rate ofN‐substituted maleimide formation wasN‐(p‐methylphenyl)maleimide>I≒II>N‐(p‐chlorophenyl)maleimide. The result was attributed to the para‐substituent effect. These imidization reaction were observed qualitatively by IR spectr

ISSN:0887-624X    

DOI:10.1002/pola.1989.080270102

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractPolymerization of 1‐aryl‐2‐trimethylsilylacetylene (aryl = thienyl, furyl, and pyridyl) was carried out by transition metal catalysts. The polymer yield was generally low due to the steric hindrance. R4Sn (R = Me,n‐Bu, Ph) exhibits some cocatalytic activities with respect to polymer yield and molecular weight. On the other hand, the polymerization was decelerated when organoaluminum compounds were used as cocatalysts. The polymer yield increased in the following order: phenyl>thienyl>furyl>pyridyl, according to the aryl substituents. The NMR (1H‐ and13C‐), IR, and UV‐visible spectra indicated that the resulting polymers have a linear conjugated polyene structure each containing the aromatic substituent and trimethylsilyl group. From1H‐NMR integration, it was found that the resulting polymers are partially desilylated depending on the substituents of monomer and the polymerization conditions. The solubility behavior, stability and fluoride‐ion induced desilylation reaction of the polymers

ISSN:0887-624X    

DOI:10.1002/pola.1989.080270103

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractThe polymerization of vinyl acetate initiated by β‐picolinium‐p‐chlorophenacylide was carried out at 30, 35, and 40°C, using the conventional dilatometric technique. The initiator and the monomer exponent values were 0.80 ± 0.15 and unity, respectively. The polymerization was inhibited in the presence of hydroquinone, but was favored by nonpolar solvent and polymerization temperature. The energy of activation was 90.3 kJ mol−1. An average value ofk p2/ktfor the present system was found to be 0.37 × 10−2L mol−1s−1. The results are explained in terms of radical mode of polymerization with degradative initiator transfer; the principal mode of termination, howeve

ISSN:0887-624X    

DOI:10.1002/pola.1989.080270104

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractAcrylonitrile (AN) has been graft copolymerized onto isotactic polypropylene (IPP) by the preirradiation method using Co60as the source of gamma rays in the presence of ethanol,n‐propanol, isopropanol,n‐butanol,tert.butyl alcohol, andn‐pentanol. Alcohols vary in their ability to influence grafting of AN onto IPP and the following reactivity order was found:n‐pentanol>n‐butanol>tert.‐butanol>n‐propanol>ethanol>isopropanol. An attempt has been made to explain the observed reactivity pattern shown by different alcohols. Thermal behavior of the graft copolymer has been compared with that of IPP and irradiated IPP and it was observed that grafted IPP is thermally more stable than IPP and i

ISSN:0887-624X    

DOI:10.1002/pola.1989.080270105

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractThe photoprotective effectiveness of various polymeric and nonpolymeric hindered amine light stabilizers (HALS) was determined by exposing samples of high‐density polyethylene (HDPE) containing these additives to ultraviolet (UV) light and measuring the resultant oxygen uptake characteristics. Values of the initial quantum yield for oxygen uptake calculated for these formulations indicate that the higher molecular weight HALS compounds are less effective photostabilizers than the nonpolymeric HALS, and this is partly attributable to their decreased mobility in the polymer matrix. It was further found that the addition of an ultraviolet absorber (UVA) to a formulation containing a polymeric HALS compound enhances its photostability, although this phenomenon may be partly due to synergism between the UVA and the antioxidant, the latter having been added as part of the base stabilization. The antagonism which exists between certain sulfur‐containing antioxidants and HALS compounds was also investigated and it was found that the lower molecular weight sulfur‐containing antioxidants exhibit the greatest degree of antagonism. The results confirm that the mobility in the polymer matrix of the stabilizer system can serve as an explanation of its effectiveness. The article provides evidence that the technique of oxygen uptake monitoring is a sensitive and rapid method of assessment of polymer photostability in the presence of stabilizer sy

ISSN:0887-624X    

DOI:10.1002/pola.1989.080270106

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractThe catalytic activity of a series of [Rh L‐L chel]X complexes, in which we have varied the unsaturated ligand [L‐L =cis, cis‐cycloocta 1,5‐diene(cod) or 2,5‐norbornadiene(nbd) the nitrogen chelating ligand [chel = 2,2′‐bipyridine(bipy), 2,2′‐dipyridylamine(dipyam), 2,2′‐bipyrazine (bipz), 4,4′‐dimethyl‐2,2′‐bipyridine (4,4′‐Me2bipy)] and the counter ion [X = PF6, ClO4, BPh4], has been examined in reactions with phyenylacetylene (PA). The catalytic behaviour of the [Rh(cod)Cl2],tmeda (tmeda = N,N,N′,N′tetramethylethylendiamine), [Rh(cod)Cl2],teda](teda = triethylendiamine), of the dimer [Rh(cod)Cl]2, and the use of NaOH as cocatalyst in different reaction conditions was also examined. The influence of the ligands on the catalytic activity of these RhIcomplexes is discussed.1H and13C NMR spectra have shown that highly stereoregular polyphenylacetilene can be obtained. Conditions for homogeneous doping of PPA, to obtain materials whose conductivity varies over 10–11 magnitude orders, are proposed. The stabilit

ISSN:0887-624X    

DOI:10.1002/pola.1989.080270107

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractThe rate constants of hydrolysis of the enantiomers of amino acid nitrophenyl esters by catalytic domains composed of cationic surfactant aggregates and dipeptide catalysts orNdecanoyl‐L‐histidine have been determined at pH 7.30. The dipeptide catalysts shows large rate enhancement and stereoselectivity in aggregate domains. The surfactant structural effects are examined by investigation of the rate constants and stereoselectivities, and the nature of stereoselective catalysis is discus

ISSN:0887-624X    

DOI:10.1002/pola.1989.080270108

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractPolynucleotide analogs with polytrimethylenimine backbones and optically active 2‐(thymin‐1‐yl)propionic acids as pendants were prepared. Linear polytrimethylenimines were obtained by ring‐opening polymerization of 2‐phenyl‐5,6‐dyhydro‐4H‐1,3‐oxazine and subsequent hydrolysis of the resulting polymers. 2‐(Thymin‐1‐yl)propionic acids were reacted withN‐hydroxy succinimide to form active esters. Optical purities of active esters were determined by NMR with chiral chemical shift reagents. The polynucloetide analogs and related monomer and dimer model compounds were prepared by grafting re

ISSN:0887-624X    

DOI:10.1002/pola.1989.080270109

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractCopolymers of isobutylene with 1,4‐13C‐isoprene have been prepared in methyl chloride solvent at −90 to −50°C using aluminum chloride and organoaluminum halide initiators. The examination of these copolymers containing 0.5 to 3.0 mol % of the diolefin by13C‐NMR has given new information about the mechanism of the copolymerization. It appears that every macromolecule ends in an isoprene derived unit; that chain transfer to monomer by an isoprene‐derived propagating carbocation is the dominant chain breaking process. The copolymer triad sequences have been unambiguously assigned and analyzed in both batch and continuous stirred tank reactor copolymers. The relative concentrations of the triads agree with those predicted by published react

ISSN:0887-624X    

DOI:10.1002/pola.1989.080270110

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY