摘要:

AbstractFour different polyimides have been studied by thermogravimetry to ascertain their relative thermal stabilities in both inert and oxidising atmospheres. Experiments have been carried out at a rate of temperature rise of 2°C min−1and isothermally at a number of temperatures in order to calculate overall activation energies for breakdown. The polymers have also been examined by pyrolysis‐gas chromatography‐mass spectrometry using two different procedures. In the first, fresh samples were pyrolysed at a number of increasing temperatures, whereas in the second, the same sample was subjected to successive pyrolyses at the same temperature intervals. The results are compared with those of other workers derived using different tech

ISSN:0007-1641    

DOI:10.1002/pi.4980190311

出版商:John Wiley&Sons, Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractCopolymers of 5‐isopropenyl‐ and 5‐vinyl‐1,3,4‐oxathiazol‐2‐ones with styrene and methyl methacrylate have been prepared and characterised by elemental analysis, g.p.c., i.r. and13C n.m.r. spectroscopy. On heating at 135–140°C the copolymers undergo thermal decarboxylation affording polymer‐bound nitrile sulphides, which may be trapped as their 1,3‐dipolar cycloadducts with dimethyl acetylenedicarboxylate, ethyl propiolate, ethyl cyanoformate, diethyl fumarate and chloral. The products are identified as terpolymers comprising units of styrene or methyl methacrylate, methacrylonitrile or acrylonitrile, and the respective heterocyclic cycloadducts [isothiazoles(3) and (7), l,2,4‐thiadiazole(8), isothiazoline(10), and 1,3,4‐oxathiazole(12)]. In the absence of a dipolarophile the oxathiazolone units are converted to nitriles. Treatment of polymeric ethyl thiadiazolecarboxylate(8c) with 1‐aminobutane yields amide(14c). On heating copolymer(12c) at 165°C in the presence of ethyl cyanoformate, thiadiazole(8c) is formed, presumably via cycloreversion to polymeric nitrile sulphide followed by cycloaddition to the nitrile. An alternative approach to copolymers incorporating isothiazoles and 1,2,4‐thiadiazoles is provided by copolymerisation of their 3‐isoprop

ISSN:0007-1641    

DOI:10.1002/pi.4980190312

出版商:John Wiley&Sons, Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractThe g.p.c. analysis of nitrate and tricarbanilate derivatives of cellulose is described for the determination of molecular weight distribution. The method uses macroreticular poly(styrene‐divinylbenzene) packing materials with tetrahydrofuran as eluent. The full molecular weight distribution analysis with a three‐column system takes less than 30 min, making the method additionally suitable for the monitoring of industrial nitration processes. A simpler two‐column system is also described which is suitable for the analysis of lower molecular weight materials with improved resol

ISSN:0007-1641    

DOI:10.1002/pi.4980190313

出版商:John Wiley&Sons, Ltd    

年代:1987

数据来源: WILEY

摘要:

Abstract2,2′‐Azo‐bis‐isobutyronitrile (AIBN), enriched in its methyl groups with carbon‐13, has been used to initiate copolymerizations at 60°C of 2‐vinylpyridine (2VP) with methyl methacrylate (MMA). Examination by13C n.m.r. of the end groups in the copolymers indicates that 2VP is 2–4 times as reactive as MMA towards the 2‐cyano‐2‐propyl radical. The presence of either 4‐styrylpyridine of 2,6‐distyrylpyridine in MMA or styrene causes considerable alteration of the13C n.m.r. signals from C6H513COO—end groups in polymers prepared at 60°C using benzoyl peroxide as initiator but has no effect on the signals from (13CH3)2C(CN)— end groups derived from AIBN. It is deduced that the styrylpyridines are rather reactive towards the benzoyloxy radical but are unreactive towards

ISSN:0007-1641    

DOI:10.1002/pi.4980190314

出版商:John Wiley&Sons, Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractN‐Vinylcarbazole was homopolymerised or was copolymerised with divinylbenzene (2% and 4%) using AIBN as initiator. The linear homopolymer was shown not to undergo direct lithiation using n‐butyllithium, but lithiation was achieved using n‐butyllithium and brominated linear poly(N‐vinylcarbazole). The polymers reacted smoothly with mercury (II) acetate or trifluoroacetate in THF or dichloromethane to give mercuriated polymers with high degrees of substitution (approx. 80%); with thallium (III) trifluoroacetate in dichloromethane a thalliated polymer was formed, but with a lower degree of substitution (approx. 20%). The mercuriated and thalliated polymers reacted with iodine (or potassium iodide) to give polymers containing an iodo‐substituent. All the metallated polymers reacted with borane to give polymer‐supported organoboranes which, on treatment with water or alkaline hydrogen peroxide, gave polymers containing boronic acid residues or phenolic residues, respectively. The lithio‐substituent in the linear polymer was converted into chloromercury and carboxyli

ISSN:0007-1641    

DOI:10.1002/pi.4980190315

出版商:John Wiley&Sons, Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractRadical copolymerisations of maleic anhydride andtrarcs‐stilbene have been carried out in methyl ethyl ketone at 60°C using 2,2′‐azo‐bis‐isobutyronitrile as initiator. The copolymers formed at all feeds are slightly rich in maleic anhydride units but are heterogeneous with regard to both composition and molecular weight distribution. It is concluded that this effect is probably produced by phase separation during the copolymerisation and that any interpretation of copolymerisation rates or copolymer compositions in terms of mechanism is not strai

ISSN:0007-1641    

DOI:10.1002/pi.4980190316

出版商:John Wiley&Sons, Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractA 52:48 mixture ofsyn‐ andanti‐7‐ethylbicyclo[2.2.1]hept‐2‐ene was submitted to polymerization by five metathesis catalysts: RuCl3. 3H20, IrCl3.3H2O, (mes)W(CO)3/EtAlCl2/norbornene epoxide, WCl6/Me4Sn, and ReCl5. Only theantiisomer undergoes ring‐opening polymerization, from which it is concluded that propagation occurs by attack on the exo face. The fraction ofcisdouble bonds and tacticities were determined from13C n.m.r. spectra of the polymers and their hydrogenated products. For the unsaturated polymers these were respectively: 0 00 atactic, 0 21 atactic, 0 43 tactic (c/r, t/m), 059 atactic, 1 00 syndiotactic. The atactic polymers all show a bias towardsmdyads for bothcisandtransdouble bonds. This indicates an influence of the configuration of the polymer chain attached to the propagating metal‐carbene complex on the stereochemistry of additi

ISSN:0007-1641    

DOI:10.1002/pi.4980190317

出版商:John Wiley&Sons, Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractA series of poly(diphenyl itaconate)s, in which the phenyl ring has been substituted in theparaposition by alkoxy units containing up to seven carbon atoms, has been synthesised and characterised. Glass transition temperatures were observed to decrease as the number of atoms in thep‐substituent rose to six, but increased when the chain became longer. Heat capacity changes, ΔCP, atTgwere measured and the value of the Wunderlich parameter ΔCp/bead was found to lie between 7 0 and 10 3 JK−1mol−1depending on the size of the alkoxy unit. Dynamic mechanical analysis revealed up to three sub‐glass‐transition damping peaks centred on 290 K, 200 K and 110 K. These have been assigned respectively to (a) oxycarbonyl group rotation, (b) motion involving the pendant phenyl rings and (c) limited bond reorientation in thep‐alkoxy groups when these contain four

ISSN:0007-1641    

DOI:10.1002/pi.4980190318

出版商:John Wiley&Sons, Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractHigh molecular weight poly(n‐butyl α‐cyanoacrylate) has been obtained by zwitterionic polymerization. This polymer exhibits sensitivity to an electron beam (20 keV) about 25 times higher than that of PMMA, with a contrast of 3, and a sensitivity to X‐rays (λ = 13−34 Å) about 15 times higher than that of PMMA, with a contr

ISSN:0007-1641    

DOI:10.1002/pi.4980190319

出版商:John Wiley&Sons, Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractThe coupling of polymers bearing mutually reactive groups is generally prevented by the low concentration of end‐groups and the immiscibility of the polymers. This can be overcome by an interfacial technique concentrating the reactive groups in the interfacial region. This paper focuses on the effect that an end‐group has on the behaviour of a polymer of opposite philicity at a water‐toluene interface. Measurements of the reduction in interfacial tension promoted by poly(ethylene oxide) (PEO) end‐capped by a hydrophobic C10H18group, and polystyrene (PS) terminated by an ammonium bromide group shed light on the role played by the end‐group in the polymer adsorption. Values of the equilibrium interfacial tension support the conclusion that the adsorption of the hydrophilic polymer (PEO) is largely independent of the C10H18end‐group whereas the ammonium bromide effectively drives PS to the interfa

ISSN:0007-1641    

DOI:10.1002/pi.4980190320

出版商:John Wiley&Sons, Ltd    

年代:1987

数据来源: WILEY