摘要:

Although ortho-esters constitute a well-known class of organic compounds, the orthoacrylates were unknown prior to a report from these laboratories in 1972. To date, this novel class of acrylic esters has not been investigated as polymerization monomers. We report here polymerization and copolymerization studies of representative members of this class of compounds. Although the orthoacrylates studied did not polymerize in the presence of conventional cationic initiators nor radical initiators, they did respond to radical-initiated copolymerization with a variety of conventional vinyl monomers. Their corresponding reactivity ratios were determined, as well as the Q and e parameters. Monomer syntheses and characterization are reported, as well as structural and properties studies on the copolymers.

ISSN:0022-233X    

DOI:10.1080/00222338508063313

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Cyclopropenone ketals have been shown to undergo radical-initiated copolymerization with several conventional comonomers, and their corresponding reactivity ratios were calculated. Low reactivity ratios were obtained and were attributed to steric inhibition of propagation. The structure of the copolymers was elucidated through spectral analysis and chemical modification. Participation of a charge-transfer complex was suggested in the copolymerization of 6,6-dimethyl-4,8-dioxaspiro(2. 5)oct-1-ene and N-vinylpyrrolidone. The complex was detected in the UV spectrum, and the equilibrium constant for complexation was determined by NMR techniques. Copolymerization between a 1:1 charge-transfer complex and nonassociated acceptor was proposed to account for a 2:1 incorporation of acceptor to donor in the copolymer.

ISSN:0022-233X    

DOI:10.1080/00222338508063314

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The effect of phosphorylated poly(2,6-dimethyl-l,4-phenylene oxide) (PPOP) on the stability of high-density polyethylene (HDPE) is described. One and 5% (w/w) of PPOP was melt blended with HDPE (Samples A1and A5, respectively). The samples were extruded in ribbon form and irradiated with UV light for several hours. In the presence of PPOP, suppression of double bond formation in HDPE was indicated by IR spectroscopy. HDPE became very brittle after 2 5 h irradiation, while Samples A1and A5showed much better retention of mechanical properties. The limiting oxygen index of HDPE did not change by incorporation of PPOP. The effect of thermal aging at 100°C on the mechanical properties of HDPE and Samples A1and A5was also studied.

ISSN:0022-233X    

DOI:10.1080/00222338508063315

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The atmospheric aging process in plasma-polymerized organosilicon thin films was studied. The investigations were carried out for plasma polymers produced from methylsilane, methylsilazane, and methylsiloxane, structurally different monomers. ATR-IR spectroscopic examinations revealed the strong effect of aging on the films structure. The formation of ‒OH, >C˭0, Si‒O‒Si, and Si‒O‒C groups and the decay of SiH groups were found to be general trends in the structural changes of the plasma polymers investigated that resulted from aging. Mechanisms of the reactions contributing to the aging process were discussed. Kinetic studies indicated that the aging process is controlled by the diffusion of atmospheric oxygen and water into the film. Wettability data showed that aging produces distinct changes in the surface energy components of the films, increasing the dispersion component and decreasing the polar component. This trend was consistent with the structural changes observed for aged films.

ISSN:0022-233X    

DOI:10.1080/00222338508063316

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Various 4,4′ -bis(N2-[4-(4-aminophenoxy)phenyl]aspartimido)diphenylmethane-type bisaspartimide-diamines have been used as solventless curing agents for epoxy resins. The thermal curing was performed at 170, 190, and 230°C to give a tough brown polymer. Thermogravimetric analysis of the polymer obtained showed thermal stability up to 330°C and char yields of 45% in N2at 800°C and 12% in air at 700°C. The thermal curing reaction was monitored using FT-IR. The synthesized polymers are useful for making composites, laminates, and adhesives.

ISSN:0022-233X    

DOI:10.1080/00222338508063317

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Polyimides have been synthesized from pyromellitic dianhydride, 3,3′,4,4′-benzophenone tetracarboxylic dianhydride, and bis(p-aminophenyl) alkane diamines using a two-step method. All the polycondensation reactions were carried out in dimethyl acetamide under identical reaction conditions. The poly(amic acids) obtained in the first step had inherent viscosities of 0.39–0.93 and were thermally converted to polyimides. The thermal stabilities of these polyimides were measured by dynamic thermogravimetry in air. Properties of the methyl-substituted polyimides are compared with those of unsubstituted ones. The introduction of a methyl group into the polymeric chain led to a decrease in the inherent viscosity and the thermal stability.

ISSN:0022-233X    

DOI:10.1080/00222338508063318

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Ultraviolet absorption and fluorescence spectra of methyl salicylate, isomers of methyl salicylate derivatives, and polymers with units of isomers of methyl salicylate have been investigated. The λmaxof methyl salicylate and its derivatives is centered around 310 nm. When the phenolic hydroxyl group is acetylated, the maximum is at 285 nm. Fluorescent emission maxima depend on the excitation wavelength. Two groups of maxima centered at 350 and 460 nm indicate that two molecular species (already present in the ground state) of the methyl salicylate moiety, probably tautomers, play essential parts as photoexcited states in the photophysics of methyl salicylate derivatives.

ISSN:0022-233X    

DOI:10.1080/00222338508063319

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The surface structures of low-density polyethylene (LDPE) film exposed to plasma or γ-ray in air were characterized by ESCA, IR, and EMS. The formation of trans C˭C bond on the LDPE film surface was observed by the exposure to ac air plasma (2 × 10−2torr, 19 W plasma power). Large amounts of O and N atoms as an amide structure were incorporated into the polymer surface by the plasma treatment. These plasma reactions occurred mainly in the amorphous region, and the polymer surface became rough enough to have a microdomain structure upon increasing the plasma treatment time up to 3 h. γ-Irradiation of LDPE in air only brought about O-atom incorporation as ketone and ether linkages. The polymer surface did not undergo etching under γ-irradiation as it did in plasma treatment.

ISSN:0022-233X    

DOI:10.1080/00222338508063320

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The kinetics of vinyl polymerization of methyl methacrylate initiated by the Ce(IV)/thioglycerol couple were investigated in an aqueous system in the temperature range 5–20°C. The rate of polymerization, the rate of Ce(IV) disappearance, etc. were measured at various concentrations of the monomer, thioglycerol (TG), and eerie ion. The effect of some electrolytes and organic nitrogen compounds, presumed to behave as ideal retarders or inhibitors, has been investigated. The proposed reaction scheme involves initiation by an organic free radical produced by direct interaction of Ce(IV) with the activator (TG) and termination by Ce(IV). Various rate parameters have been evaluated.

ISSN:0022-233X    

DOI:10.1080/00222338508063321

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Homogeneous polymerization of methacrylamide initiated by the ceric ammonium sulfate-citric acid (CA) redox pair has been investigated and reported at 35 ± 0.2°C under nitrogen atmosphere. The initiation was caused by the free radical generated by the decomposition of the complex formed between ceric ion and citric acid. The rate of monomer disappearance was found to be proportional to [CA]0.4, [Ce0.4+]0.65, and [Monomer]1The rate of ceric ion disappearance was directly proportional to the ceric ion concentration but independent of the monomer concentration. The initial rate was independent of [H2SO4]. The activation energy of the system was found to be 21.4 kJ/mol.

ISSN:0022-233X    

DOI:10.1080/00222338508063322

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor