摘要:

AbstractThe anionic polymerization of 2‐ethylhexyl acrylate (EtHA) initiated with the complex butyllithium/lithium‐tert‐butoxide (BuLi/t‐BuOLi) was investigated at −60°C in a medium of various solvating power, i.e., in mixtures of toluene and tetrahydrofuran and in neat tetrahydrofuran. With increasing amount of THF in the mixture the attainable limiting conversion of polymerization decreases; the monomer can be polymerized quantitatively only in a toluene/THF mixture (9/1). Molecular weights of the polymers thus obtained, their distribution, and initiator efficiency are not appreciably affected by the polymerization medium. The molecular weight distribution of the products is medium‐broad (Mw/Mn= 2–2.4), with a hint of bimodality. The1H‐13C‐NMR, and IR spectra suggest that during the polymerization there is neither any perceptible reesterification of the polymer with the alkoxide nor transmetalation of the monomer with the initiator. In a suitable medium, autotermination of propagation proceeds to a limited extent only, predominantly via intramolecular cyclization of propagating chains; in a medium with a higher content of polar THF, it prevails and terminates propagation before the polymerization of the monomer has been completed. © 1992 J

ISSN:0887-624X    

DOI:10.1002/pola.1992.080300801

出版商:John Wiley&Sons, Inc.    

年代:1992

数据来源: WILEY

摘要:

AbstractThe polymerization of 2‐ethylhexyl acrylate (EtHA) initiated with lithium‐tert‐butoxide (t‐BuOLi) in tetrahydrofuran (THF) and in the temperature range between −60 and 20°C was investigated. The reaction rate is distinctly temperature‐dependent and at −60°C is already very low, similarly to the polymerization of methacrylates. Molecular weights of the polymers thus formed, particularly at higher temperatures, are inversely proportional to conversion of the monomer due to the slow initiation reaction. This is documented by the low consumption of alkoxide even at long reaction times, which also depends on the reaction temperature. At higher temperatures the polymerization stops spontaneously, due to the greater extent of autotermination reactions. The weak initiating efficiency of the alkoxide decreases still more with decreasing concentration of the monomer during the polymerization, as confirmed by the concentration dependence of the reaction rate in toluene at −20°C. The results suggest a negligible initiating effect of alkoxides in complex bases, particularly at lower polymerization temperatures. © 1992 J

ISSN:0887-624X    

DOI:10.1002/pola.1992.080300802

出版商:John Wiley&Sons, Inc.    

年代:1992

数据来源: WILEY

摘要:

AbstractThe effect of polymer matrices on a photoinduced rearrangement process has been shown to be dependent upon whether the photoreactive group is attached to a polymer backbone, or free. If diphenylcarbonate is simply embedded in a polymer matrix, the rearrangement process is independent of whether the host film is above or below its glass transition. However, if the diphenylcarbonate group is incorporated as part of a polycarbonate backbone, the Fries rearrangement process is significantly reduced for photolyses conducted at temperatures well below the glass transition of polycarbonate. The utility of fluorescence spectroscopy in identification of the initial salicylate type photo‐Fries type rearrangement product of polycarbonate is also demonstrated. The broad, structureless fluorescence spectrum with peak maximum at 470 nm produced by photolysis of polycarbonate films for short time periods is assigned to emission from phenyl salicylate type photoproducts. © 1992 John Wiley&Sons, I

ISSN:0887-624X    

DOI:10.1002/pola.1992.080300803

出版商:John Wiley&Sons, Inc.    

年代:1992

数据来源: WILEY

摘要:

AbstractPoly(2,4‐dichloro‐6‐vinyl‐1,3,5‐triazine‐co‐styrene)s were prepared by the reaction of poly(2,4‐diamino‐6‐vinyl‐1,3,5‐triazine‐co‐styrene)s with hydrochloric acid, and followed by treatment with thionyl chloride andN,N‐dimethylformamide. The chlorine atoms in the resulted polymers were replaced readily by several nucleophiles such as amide, alkoxide, and mercaptide to afford the corresponding polymers in moderate yields. Among these, polymers containing oligo (oxyethylene) groups at both 2 and 4 positions of 1,3,5‐triazine ring worked effectively as phase transfer catalysts for the reaction ofn‐octyl bromide with alkali metal thiocyanates in toluene–water systems. However, polystyrenes containing only one oligo (oxyethylene) group in monomer unit scarcely exhibited the activity under these conditions although the degree of loading of the functional group was almost the same. The activity depended on the number of oxyethylene units, and the selectivity to alkali metal ions was also ob

ISSN:0887-624X    

DOI:10.1002/pola.1992.080300804

出版商:John Wiley&Sons, Inc.    

年代:1992

数据来源: WILEY

摘要:

AbstractGraft polymerizations of mixtures of methacrylonitrile withn‐alkyl methacrylales onto amylomaize were carried out. The graft copolymers were characterized by both IR and13C‐NMR spectroscopies. The influence of the monomer feed on the grafting parameters has been studied. The variation of these parameters with the mole fraction of methacrylate in the feed for the first three systems studied, MAN/MMA, MAN/EMA and MAN/BMA, was similar: thus, percent grafting (%G, percent weight of grafted polymer with respect to grafted amylomaize), percent grafted amylomaize (%GA, percent weight of grafted amylomaize with respect to initial amylomaize), percent grafting conversion (%Cg, percent weight of grafted polymer with respect to initial monomer), and percent total conversion (%Ct, percent weight of total acrylic polymer with respect to initial monomer) were increased, but percent grafting efficiency (%GE, percent weight of graft copolymer with respect to total polymer) decreased. The system MAN/HMA presented values of grafting parameters lower than those of the previous systems. The optimum values were obtained at 0.6 HMA mole fraction in the monomer feed. When the number of carbon atoms of then‐alkyl group rises from 1 to 4, the increase of then‐alkyl group length gives rise to increases of the %G %Cgand %Ctvalues and decreases of the %GE and %GA values. For the largest methacrylate, the grafting reaction appears to be controlled by the lesser accessibility of the monomer to the active sites of the carbohydrate. © 1992 John Wiley&S

ISSN:0887-624X    

DOI:10.1002/pola.1992.080300805

出版商:John Wiley&Sons, Inc.    

年代:1992

数据来源: WILEY

摘要:

AbstractViscometric measurements on aqueous solutions of the strongly acidic polyelectrolyte, poly(2‐acrylamido, 2‐methyl propane sulphonic acid) (PAS), have shown the necessity to include salt at a very high concentration in order to screen the charges. PAS was found to dissolve in formamide, but the properties of the isolated polymer demonstrated the occurrence of chemical changes during the dissolution process. Several procedures proved the conversion of sulphonic acid moieties to sulphonamide groups to an extent depending on the time and temperature of dissolution. At elevated temperature and extended times dissolution afforded complete conversion, i.e., a solution in formamide of a new neutral polymer, poly(2‐acrylamido, 2‐methyl propane sulphonamide) (PASAM), which does not require the inclusion of salts. By light scattering, the degree of polymerization of this PASAM was shown to be the same as that of the original PAS. The viscometric behavior of the PASAM in salt‐free water was that of a neutral polymer. Similar tests on the dissolution of the weakly acidic polyelectrolyte, poly(acrylic acid) (PAA) in formamide also showed the occurrence of amidation, but even after extended times PAA is not converted completely to polyacrylamide. © 1992 John Wiley

ISSN:0887-624X    

DOI:10.1002/pola.1992.080300806

出版商:John Wiley&Sons, Inc.    

年代:1992

数据来源: WILEY

摘要:

AbstractRadical copolymerization of dialkyl fumarates (DRF) with various vinyl monomers was carried out in benzene at 60°C. The monomer reactivity ratios,r1andr2, were determined from the comonomer‐copolymer composition curves. The relative reactivity of DRFs with various ester substituents toward a polystyryl radical was revealed to depend on both steric and polar effects of the ester groups. It has also been clarified that α‐substituents of the polymer radical have a significant role in addition of DRF, from the comparison of the monomer reactivity ratios determined in copolymerizations with monosubstituted and 1,1‐disubstituted ethylenes. The absolute cross‐propagation rate constants were also evaluated and discussed. © 1992 John Wiley

ISSN:0887-624X    

DOI:10.1002/pola.1992.080300807

出版商:John Wiley&Sons, Inc.    

年代:1992

数据来源: WILEY

摘要:

AbstractFour aryl dichlorides containing secondary amide structural units as monomers were synthesized from substituted piperazines and chlorobenzoyl chlorides. Polyamides were prepared by the nickel‐catalyzed coupling polymerization of these monomers. Polymerizations were carried out inN‐methyl‐2‐pyrrolidinone (NMP) in the presence of nickel chloride, zinc, triphenylphosphine, and bipyridine, and resulted in polyamides with inherent viscosities up to 0.38 dL/g under mild conditions. The structure of polymer was determined by IR and13C‐NMR spectroscopies. The polyamide, poly[4,4′‐biphenyldicarbonyl (2,5‐dimethylpiperazine)]6d, was readily soluble in dipolar aprotic solvents and chloroform. Thermogravimetry of polyamides, poly[(4,4′‐biphenyldicarbonyl piperazine)]s6, showed 10% weight loss at around 425 and 450°C in air and under nitrogen, respectively. © 1992

ISSN:0887-624X    

DOI:10.1002/pola.1992.080300808

出版商:John Wiley&Sons, Inc.    

年代:1992

数据来源: WILEY

摘要:

AbstractPolyarylates containing pendant silyl group were prepared by the phase‐transfer catalyzed, two‐phase polycondensations of 2,2‐bis (4‐hydroxyphenyl) propane with corresponding dicarbonyl chlorides such as 2‐trimethylsilylterephthaloyl chloride, 5‐trimethylsilylisophthaloyl chloride, 5‐dimethylphenylsilylisophthaloyl chloride, and 5‐triphenylsilylisophthaloyl chloride. The resulting amorphous polyarylates with glass transition temperatures of 163–214°C had inherent viscosities in the range of 0.41–0.95 dL/g. These polyarylates were readily soluble in common chlorinated hydrocarbons and it was possible to obtain transparent, flexible, and tough films from the polymer solutions. The prepared polyarylates showed fairly good thermal stabilities as well as tensile strengths, i.e., the tensile strengths of the cast films from chloroform solution were 6.0–6.7 kg/mm2. And TGA data revealed 10% weight losses and residual weights at 800°C were 437–495°C and 27–40% under nitrogen atmosphere, respectively.

ISSN:0887-624X    

DOI:10.1002/pola.1992.080300809

出版商:John Wiley&Sons, Inc.    

年代:1992

数据来源: WILEY

摘要:

AbstractIn order to improve the solubility of aromatic polyamides without significant loss of thermal stability, synthesis of aromatic polyamides containing pendant silyl groups was carried out by direct polycondensation of silylated aromatic diacids such as 2‐trimethylsilylterephthalic acid (TSTA), 2,5‐bis (trimethylsilyl) terephthalic acid (BTSTA), 5‐trimethylsilylisophthalic acid (TSIA), 5‐dimethylphenylsilylisophthalic acid (DMSIA), and 5‐triphenylsilylisophthalic acid (TPSIA) with various aromatic diamines. The resulting polyamides had inherent viscosities in the range of 0.18–1.10 dL/g and showed improved solubilities toward aprotic polar solvents such as NMP, DMF, DMSO, etc. The prepared aromatic polyamides exhibited fairly good thermal stabilities, which were almost comparable to those of corresponding nonsubstituted aromatic polyamides. That is, thermogravimetric analysis (TGA) data revealed 10% weight losses at 358–500°C and residual weights at 700°C were 46–67% under nitrogen atmosphere. © 1992 Jo

ISSN:0887-624X    

DOI:10.1002/pola.1992.080300810

出版商:John Wiley&Sons, Inc.    

年代:1992

数据来源: WILEY