摘要:

AbstractA novel class of polymer precursors of the general formula,where A is an aromatic structure bearing amide or imide linkages, were synthesized. More particularly, 4‐aminoacetophenone was condensed with malononitrile to afford 4‐amino‐α‐methyl‐β,β′‐dicyanostyrene (1). The condensation of the latter with half molar amount of terephthaloyl dichloride, pyromellitic dianhydride, or benzophenone tetracarboxylic dianhydride yielded the polymer precursors. In addition, compound1was condensed with an equimolar amount of maleic anhydride to afford the corresponding maleimide. The monomers were characterized by elemental analyses, FT‐IR,1H‐NMR, and DTA. Crosslinked resins were obtained upon curing the monomers at 300°C for 72 h. They were stable up to 381‐422°C in N2or air and afforded anaerobic char yields of 64‐68% at 800°C.

ISSN:0887-624X    

DOI:10.1002/pola.1994.080321001

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe thermal degradation Processes which occur in poly(phenylenesulfide) (PPS) have been studied by direct pyrolysis‐mass spectrometry (DPMS). The structure of the compounds evolved in the overall temperature range of PPS decomposition (400–700°C) suggests the occurrence of several thermal decomposition steps. At the onset of the thermal degradation (430–450°C) this polymer decomposes with the formation of cyclic oligomers, generated by a simple cylization mechanism either initiated at the—SH end groups or by the exchange between the inner sulfur atoms along the polymer chain. At higher temperature (>500°C) another decomposition reaction takes over with the formation of aromatic linear thiols. The formation of thiodibenzofuran units by a subsequent dehydrogenation reaction occurs in the temperature range of 550–650°C; in fact, pyrolysis products with a quasi‐ladder structure have also been detected. Ultimately, above 600°C, extrusion of sulfur from the pyrolysis residue occurs with the maximum evolution at the end of decomposition (about 700°C). It appears, therefore, that the residue obtained at high temperature tends to have a crosslinked graphite‐like structure from which the bonded sulfur is extruded. © 1994

ISSN:0887-624X    

DOI:10.1002/pola.1994.080321002

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractDimensionless equilibrium constants describing the self‐association of the hexafluoro‐2‐alkyl‐2‐propanol group have been determined from infrared spectroscopic data. Corresponding values of these equilibrium constants for a fully modified polyisoprene containing the hexafluoroisopropanol group (PHFPI) were calculated by taking into account differences in the molar volume of the model and the specific repeat unit of the polymer. Equilibrium constants describing the inter‐association of PHFPI with methacrylate, acrylate, and acetoxy type carbonyl groups were obtained from spectroscopic studies of miscible PHFPI blends with poly(n‐butyl methacrylate), poly(methyl acrylate), and an ethylene‐co‐vinyl acetate copolymer containing 70 wt% vinyl acetate. The set of equilibrium constant values were then used to calculate theoretical miscibility windows for the complete range of PHFPI blends with poly(n‐alkyl methacrylate)s and four copolymers, ethylene‐co‐methyl methacrylate, styrene‐co‐methyl acrylate, ethylene‐co‐methyl acrylate, and ethylene‐co‐vinyl acetate. Experimental infrared studies confirm the general validity of the predicted miscibility w

ISSN:0887-624X    

DOI:10.1002/pola.1994.080321003

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractPlasma treatment of a polymeric surface could involve at least three major mechanisms: (1) direct interaction of reactive species in the low‐temperature plasma state with the surface (line of sight irradiation effect), and (2) chemical reactions of plasma‐induced reactive species with the surface, and (3) reactions among reactive species and the surface (plasma polymerization). The first and the third effects are considered to be limited to the surfaces which directly contact with plasma (glow). The second effect is not limited to the surfaces that contact with plasma state but can penetrate beyond the plasma zone by diffusion. Using an assembly of fibers, of which only the top layer contacts with plasma (glow), the penetration of chemical changes caused by plasma exposure was investigated. Results indicate that the fluorination effect (incorporation of fluorine‐containing moieties on the surface of polymeric substrate) penetrates through a considerable thickness of the assembly of fibers, depending on the porosity (gas permeability) of the system. Chemical reactions of plasma‐induced (chemically) reactive but nonpolymerizing species with the substrate fibers seems to predominate. The direct interactions of energetic species, such as ions, electrons, and electronically excited species, with polymeric surfaces seems to play relatively minor roles in the plasma treatment investigated. The major role of plasma, in this case, seems to be creating such chemically reactive species. © 1994 John Wiley&S

ISSN:0887-624X    

DOI:10.1002/pola.1994.080321004

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe depth of surface modification by low‐temperature cascade arc torch is investigated. A stack of 10 sheets of nonwoven fabrics of polyester fibers is exposed to a low‐temperature cascade arc torch containing CF4or C2F4, and the fluorination effect is examined by ESCA. It is shown that interaction of chemically reactive species, created in a low‐temperature cascade arc torch, with the surface is not limited to the surface contacted by the torch (flame). The results indicate that the fluorination effect is observed on surfaces which are shadowed from the torch by overlying fibers. The highest degree of fluorination is found on the second layer, rather than on the first layer which the torch contacts directly. No significant differences in the trends of penetration of CF4and C2F4treatment through porous samples are observed. However, ESCA data show principal differences in chemical structures of the surfaces treated with CF4(nonpolymer‐forming gas) and C2F4(polymer‐forming gas). These results indicate that chemically reactive species induced by the excited species of argon rather than primary species created by the ionization process seem to play predominant roles in the surface treatment as well as the low‐temperature cascade arc torch polymerization of perfluorinated compounds. © 1994 John Wil

ISSN:0887-624X    

DOI:10.1002/pola.1994.080321005

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractSiloxane urethane block copolymers were prepared with siloxanes as the soft segment. Films were cast from a variety of solvents. Solvent has an effect on the segregation of soft and hard segments. Surface studies, including ESCA, EDS, and FT‐IR, show well segregated block copolymers with enhanced siloxane on the surface. DSC studies show a low mp (‐44°C) for the soft segment and aTgfor the hard segment above room temperature. These materials show higher thermal stability compared to polyether urethane block copolymers. These copolymers also show relatively good resistance to exposure to oxygen plasma and show improved flame retardancy compared to nonsiliconated, polyether polyurethane block copolymers. © 1994 John Wiley&Sons

ISSN:0887-624X    

DOI:10.1002/pola.1994.080321006

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe copolymers containing photoreactive 4‐methyl coumarin pendant groups have been prepared by radical copolymerization ofN‐(1‐phenylethyl)acrylamide (M1) and 7‐acryloyloxy‐4‐methyl coumarin (M2) in DMF at 70°C. The monomer reactivity ratios (MRR) of M1and M2are estimated by Finenam‐Ross, Kelen‐Tüdos, Mayo‐Lewis, and YBR methods to be about r1= 0.12–0.16 and r2= 1.13–1.28. Dilute dioxane solutions of the copolymers (10−4‐10−5Mof 4‐methyl coumarin chromophores) are first photocrosslinked intramolecularly by irradiating 350 nm light (dimerization of 4‐methyl coumarin) and then photo‐cleaved at 254 nm (symmetric cleavage of cyclobutane). Tracing by an UV‐visible spectrophotometer, it is found that photocrosslinking and photocleavage proceed simultaneously when 254 nm is the light source and finally reaches to a dynamic equilibrium. However, only photocrosslinking can be observed under 350 nm light. Kinetic results show that both photocrosslinking and photocleavage are first‐order reactions. Moreover, photocrosslinking rate constant increases with mole fraction of M2in the copolymer (F2). On the contrary, rate constant of photocleavage decreases with in

ISSN:0887-624X    

DOI:10.1002/pola.1994.080321007

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractA series of chelating resins, derived from a macroreticular styrene‐divinylbenzene (2%) copolymer beads grafted with various poly(ethylene glycols) HO(CH2CH2O)nH(n= 0, 4, 9, 13) and containing thiol groups as chelating functions, have been synthesized in a three‐step reaction sequence. The structure of the functionalized resins was confirmed by IR spectrophotometry, elemental analysis, and differential scanning calorimetry. The complexation behavior of these thiol resins was investigated towards Hg(II), Cu(II), and Pb(II) ions in aqueous solution by a batch equilibration technique. The influence of pH on adsorption capacity was also examined. The adsorption values for metal ions' intake followed the order Hg(II)>Cu(II)>Pb(II). The affinity of these polymers towards Hg(II) ions was so high that the total mercury level in the liquid decreased from 20 ppm to below 10 ppb after 2 h of treatment. Polymers can be regenerated by washing with a solution of hydrochloric acid (6N) and 10% by weight of an aqueous solution of thiourea. © 1994 John

ISSN:0887-624X    

DOI:10.1002/pola.1994.080321008

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe types and concentrations of end groups present in bisphenol A‐tetrabromobisphenol A copolycarbonates (BA‐TBBA coPCs) have major effects on the copolymer solution washability and thermal stability. Six types of coPC end groups are possible: two by monophenol capping of each comonomer, two phenolics (BA‐OH and TBBA‐OH), and two carbamates (one from each comonomer). BA‐TBBA coPCs were prepared by typical solution and interfacial methods and their phenolic and carbamate end group concentrations were correlated with their solution washability and thermal discoloration. Both phenolic and carbamate end groups proved deleterious to these two copolymer properties. An improved interfacial process that employs 4‐N,N‐dimethylaminopyridine as the coupling catalyst provides coPCs having low concentrations of phenolic and carbamate end groups and that, therefore, wash without emulsification and are thermally stable. © 1994 John W

ISSN:0887-624X    

DOI:10.1002/pola.1994.080321009

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractExcimer lasers (ArF, λ = 193 nm, and KrF, λ = 248 nm) were used to generate polymers free of additives such as catalysts, initiators, or sensitizers. The layers obtained are of potential interest for medical applications and future molecular electronics. Dimethylpolysiloxanes and dimethylsiloxane copolymers that contain phenyl‐,n‐hexyl‐ or 3.3.3‐trifluoropropyl groups or silicon‐bound hydrogen atoms were crosslinked in the liquid phase, whereby layer thicknesses in the range from 1–300 μm were obtained. Disiloxanes and alkoxysilanes were deposited from the gas phase (LCVD, laser chemical vapor deposition) resulting in layer thicknesses below 1 μm. In almost all cases, organic layers with a smooth surface, transparency, and good adhesion were obtained on silicon as well as quartz substrates. © 1994 John

ISSN:0887-624X    

DOI:10.1002/pola.1994.080321010

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY