摘要:

AbstractWhiskers of poly(4‐hydroxybenzoate) [poly(4‐HBA)] were prepared by polycondensation of free 4‐hydroxybenzoic acid with acetic anhydride and pyridine in a high boiling inert solvent. The purity of the monomer is decisive for the success of the synthesis. For a less pure 4‐hydroxybenzoic acid, the preparation of acetylated oligomers with acetylchloride, followed by polycondensation of the isolated oligomers is a suitable alternative. Whiskers, with a solid‐solid phase transition at 364°C were obtained, which is the highest temperature reported for this transition so far. Two batches of composites were prepared from nylon‐6 using polyester whiskers with an alkaline or an acidic surface treatment. A third batch was prepared using poly(ester‐amide) whiskers. The mechanical properties of these composites indicate that the surface treatment does not play any role, and that the poly(esteramide)s are inferior to the polyester whiskers, because they are not single crystals. © 1994 John

ISSN:0887-624X    

DOI:10.1002/pola.1994.080320901

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractA novel addition polymerization of 1,4‐benzenediselenol (BDSe) to 1,4‐divinylbenzene (DVB) was carried out with various azo radical initiators [dimethyl 2,2′‐azobisisobutyrate (DAIB), 1,1′‐azobis(1‐acetoxy‐1‐phenylethane) (AAPE), and AIBN] in toluene at 65 and 75°C under a nitrogen atmosphere. The polymerization proceded without an induction period, and pale‐yellowish powder polymers were obtained in 89% yields for 75 h (DAIB), 89% yields for 24 h (AAPE), and 60% yields for 8 h (AIBN). The molecular weight (Mw) of the insoluble polymers in toluene was about 4000 (IBN) to 14,000 (DAIB or AAPE) by GPC. The polymer had an alternating structure of BDSe to DVB units by1H‐NMR, IR analyses, and selenium contents, but the polymer contained the diselenide linkage by Raman spectroscopy. By AIBN initiator, the yield of the polymers did not increase over 60% and higher molecular weight polymer was hardly obtained. According to the model addition reaction of benzeneselenol to styrene by AIBN, it was found that AIBN was consumed by the side reaction between dimethyl‐N‐(2‐cyano‐2‐propyl)ketenimine derivedAppl 11 from AIBN and benzeneselenol to give the adduct C, MH+295 by DCI MS. On the other hand, DAIB and AAPE initiators, which do not form a ketenimine intermediate, gave the polymers of higher molecular weight in a higher yield. The polymer film exhibited high refractive index (n25D= 1.81) and a reversible phase transition between a transparency and an opaque by thermal m

ISSN:0887-624X    

DOI:10.1002/pola.1994.080320902

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractSeveral well‐defined graft copolymers (7) having a water‐soluble natural polysaccharide (dextran) stock and hydrophilic polyamide branches of different molecular weights were synthesized by using a quasi‐living anionic polymerization of a bicyclic lactam1, namely by the reaction of the acyllactam group in the quasi‐living polyamide2with the hydroxyl and amino groups in the dextran derivative (6), of which the reducing end was converted to an amino group. An oligosaccharide‐terminated polyamide3was also prepared efficiently by similar coupling reaction of the corresponding quasi‐living polyamide2, with the maltose derivative (5) having an amino group. © 1994 John Wil

ISSN:0887-624X    

DOI:10.1002/pola.1994.080320903

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractNovel pH‐sensitive hydrogels containing azoaromatic crosslinks were synthesized by the crosslinking of polymeric precursors. First, a reactive polymeric precursor was synthesized by copolymerization ofN,N‐dimethylacrylamide,N‐tert‐butylacrylamide, acrylic acid, andN‐methacryloylglycylglycinep‐nitrophenyl ester. The hydrogel was prepared in the second step by the reaction of the polymeric precursor withN,N′‐(ω‐aminocaproyl)‐4,4′‐diaminoazobenzene. The hydrogels were characterized by the network structure, (that is, content of crosslinks, unreacted pendent groups, and cycles), the equilibrium swelling ratio as a function of pH, modulus of elasticity in compression, and the degradabilityin vitro. The results obtained indicated that the hydrogel network structure strongly depends on the reaction conditions such as polymer concentration, and the ratio of the reactive groups during the crosslinking reaction. The swelling and mechanical properties of hydrogels can be controlled by the modification of polymer backbone structure and/or the crosslinking density. The rates of hydrogel degradation depended on their degree of swelling. The higher the degree of swelling, the higher the degradability. The properties of the hydrogels suggest that they have a potential as carriers for colon‐specific drug delivery.

ISSN:0887-624X    

DOI:10.1002/pola.1994.080320904

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe ambifunctional monomer, 1‐propenyl glycidyl ether, was prepared from allyl glycidyl ether, by a ruthenium‐catalyzed isomerization reaction in high yield. 1‐Propenyl glycidyl ether undergoes facile photoinduced cationic polymerization to yield a crosslinked polymer. The structure of this polymer was studied using1H‐ and,13C‐NMR spectroscopies and employing well‐characterized related polymers as models. The model polymers were prepared by the cationic polymerization of allyl glycidyl ether with BF3OEt2followed by isomerization of the pendant allyl groups by a ruthenium catalyst. Subsequently, the resulting polyether‐bearing pendant 1‐propenyl ether groups was subjected to a diaryliodonium salt‐photoinitiated polymerization. A comparison of the spectra of the polymers indicated the presence of cyclic acetal units in the polymer backbone. © 1994 Jo

ISSN:0887-624X    

DOI:10.1002/pola.1994.080320905

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe photoinitiation efficiency of the fluorenone/triethylamine (TEA) system in the polymerization of methylmethacrylate (MMA) has been evaluated as a function of the monomer concentration, the amine concentration, and the polarity of the reaction medium. The polymerization proceeds readily in low polarity media (benzene/monomer), but it is negligible in more polar solvents (acetonitrile/monomer). The polymerization rate increases with the amine concentration up to 0.01MTEA. Further increase in amine concentration produces a decrease in the polymerization rate. A similar behavior was observed for the fluorenone photoreduction yield and the yield of fluorenone derived radicals. All these processes are considered to involve the excited triplet, while quenching of the excited singlet by the amine decreases the rate of these processes. However, the decrease in photoinitiation efficiency observed at high amine concentration is larger than that expected from the singlet quenching extent, as estimated from the effect of the amine on the fluorescence yield under the same experimental conditions. This discrepancy indicates that other process(es) must contribute to the protection afforded by high amine concentrations. Quenching of the charge transfer intermediate by the amine is postulated as a competitive process that could explain the above mentioned effects. © 1994 John Wiley&Sons, Inc

ISSN:0887-624X    

DOI:10.1002/pola.1994.080320906

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractA new type of membrane polymer, containing a photosensitive moiety, was synthesized. The photochemically induced functionalization and crosslinking of poly [acrylonitrile‐co‐butadiene‐co‐styrene‐co‐2‐(4‐ethenyl) phenyl‐5‐phenyl‐2H‐tetrazole], ABSV, has been studied. A variety of dipolarophiles and phenolic compounds were applied to alter the polarity of the membrane surface. The functionalization and crosslinking were initiated by photoirradiation. DSC and contact angle measurements were used to characterize the modified polymer. Pervaporation experiments with a cyclohexane/benzene mixture (5 wt% benzene) were carried out, with the results showing, that the photochemical treatment significantly effects both permselectivity and flux. Solubility parameters were found to be useful to interpret the pervaporation data. In general, the selectivity towards benzene increases with the polarity of the membrane surface, i.e., with increasing polarity of the modifier. A mechanism to explain the influence of both functionalization and crosslinking on the membrane performance, is proposed. © 1

ISSN:0887-624X    

DOI:10.1002/pola.1994.080320907

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractA series of novel bismaleimides (BMIs) were prepared from maleic anhydride and polyurethane prepolymers based on MDI (4,4′‐diphenylmethane diisocyanate) and polyether and polyester diols with various chain lengths. All the BMIs were characterized by IR,1H‐NMR, and elemental analysis. DSC studies indicated that the thermal polymerization of the BMIs could be carried out in the temperature range of 102–245°C, and that curing behavior was significantly affected by the molecular weight of the BMIs. The crosslinked BMI elastomers showed good mechanical properties and much better thermal stability than that of the traditional polyurethane elastomers. The glass transition temperatures, mechanical, and dynamic mechanical properties were dependent on the types of polyols used and the resultant crosslink densities due to various chain lengths of the BMIs. © 1994 John Wiley&

ISSN:0887-624X    

DOI:10.1002/pola.1994.080320908

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractUnsaturated perfluoroalkyl esters derived from undecylenic acid: CH2CH(CH2)8COOCH2CH2RF(with RFC6F13,2aand RFC8F17,2b) and C8F17(CH2)10COOCH2CHCH2,2cwere prepared with excellent yields. Their hydrosilylation by methylhydrodimethylsiloxane copolymers of various SiH contents gives new fluorinated polysiloxanes which were examined by1H‐ and13C‐NMR, GPC, differential scanning calorimetry, and optical polarizing microscopy. Polymers derived from compounds2aand2bexhibit mesomorphic structur

ISSN:0887-624X    

DOI:10.1002/pola.1994.080320909

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractTo improve the wettability and adhesion, graft polymerization of acrylamide (AAm) and glycidyl methacrylate (GMA) was performed onto the surface of ultra‐high modulus polyethylene (UHMPE) fiber pretreated with Ar plasma. Following the plasma treatment and the subsequent exposure to air to introduce peroxides onto the fiber surface, graft polymerization onto the UHMPE fiber was allowed to proceed from the polymer peroxides either in deaerated monomer solution at an elevated temperature (degassing method), or in aerated monomer solution containing riboflavin at 30°C under UV irradiation (photoinduction method). The monomer solution was prepared from water and dioxane for AAm and GMA, respectively. After rigorous removal of homopolymers, surface analysis of the grafted fibers was performed with ATR‐FTIR and XPS, which revealed that PAAm and PGMA chains were grafted in the surface region of fibers. The grafting rate of PAAm by the photoinduction method was much higher than that by the degassing method when compared at the same concentration of the AAm solution. The amount of PGMA grafted was greatly affected by UV irradiation time, but depended on plasma treatment time to an insignificant extent if the treatment was carried out for longer than 30 s. Reaction of propylamine with the PGMA‐grafted surface resulted in the appearance of a nitrogen peak in the XPS spectrum, suggesting the presence of epoxy groups on the surface of PGMA grafted fiber. © 1994 John Wiley&So

ISSN:0887-624X    

DOI:10.1002/pola.1994.080320910

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY