ISSN:0007-1641    

DOI:10.1002/pi.4980230102

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

ISSN:0007-1641    

DOI:10.1002/pi.4980230103

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractHighly isotactic and syndiotactic poly(methyl methacrylate)s (PMMAs) were prepared by living polymerizations in toluene witht‐C4H9MgBr andt‐C4H9Li‐R3Al (Al/Li ≧ 2), respectively. Both tactic PMMAs have the same chemical structure from the left‐end to the right‐end of the polymer chain, and narrow molecular weight distribution. Stereochemical structures at and near the chain‐ends of the isotactic PMMA could be identified with the aid of two‐dimensional NMR spectroscopy. Structural investigation on the stereoregular oligomers of MMA by NMR and X‐ray analysis provided important information on the stereoregularity of the initiation and termination processes. Block and random copolymers with high stereoregularity were prepared by these living polymerizations of MMA and ethyl methacrylate. Monomer sequence distribution and stereoregularity of the copolymers were studied by13C NMR spectroscopy and the switching point of the block copolymer could be detected. Isotactic block and random copolymers of MMA and butyl methacrylate were also prepared and analysed by on‐line GPC/NMR to give molecular weight dependence of the composition. The glass transition temperature of the copolymers of methacrylates was found to be altered in a wider temperature range by changing the tacticity as well

ISSN:0007-1641    

DOI:10.1002/pi.4980230104

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractIn this review, the synthesis and characterization of various dimeric and polymeric peroxycarbamates and azocarbamates are described in detail. These functional polymers are synthesized by stepwise capping reactions of hydroxyl terminated polyethers, polyesters or poly(butadiene) first with diisocyanates, and then with hydroperoxides or various azo compounds containing functional groups. Statistics of chain extension reactions are discussed. Kinetic parameters of thermal decomposition are reported. These functional polymers are useful for preparing block copolymers containing soft and glassy segments.

ISSN:0007-1641    

DOI:10.1002/pi.4980230105

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractMaleic anhydride (MA) reacts in acetone solution with pyridine (Py) at room temperature with carbon dioxide evolution and formation of oligomers having average M̄nranging from 400 to 700 daltons. The influence of pyridine concentration on the rate of decarboxylation has been studied. The product obtained with molar ratio MA/Py = 1.64 is very reproducible. This product has been characterized with different analytical techniques. The results obtained allowed us to propose a reaction scheme for the oligomerization

ISSN:0007-1641    

DOI:10.1002/pi.4980230106

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractPolysulfone has been carboxylated, via a metalated intermediate, by reaction of a THF solution of polymer withn‐butyllithium and then treatment with carbon dioxide. The polymer reactions withn‐butyllithium were close to quantitative and did not require the use of a tertiary amine catalyst. A series of polymers ranging from 0.2 to 1.9 carboxyl groups per repeat unit was prepared by this method in the salt, acid and ester form. The structures of these polymer derivatives were characterized by1H‐NMR,13C‐NMR and IR. The glass transition temperatures and thermal stabilities were characterized by differential scanning calorimetry (DSC) and thermogravimet

ISSN:0007-1641    

DOI:10.1002/pi.4980230107

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractThe synthesis of a series of aromatic poly(esteramide)s and the initial characterisation of these materials is reported in this paper. The polymers were prepared by transesterification polycondensation of various bis(p‐alkyl benzoate) aliphatic diamides with diols of differing lengths. Most of the polymers gave multiple endothermic peaks during heating in the DSC, and polarising optical microscopy revealed a number of different types of spherulites. X‐ray diffraction and infrared spectroscopy were used to probe the molecular correlations in the various crystalline phases. No evidence was found for liquid crystallisat

ISSN:0007-1641    

DOI:10.1002/pi.4980230108

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

Abstractω‐Dimethylaminopolystyrenes can be synthesized in quantitative yields by reacting poly(styryl)lithium with 1‐(4‐dimethylaminophenyl)‐1 ‐phenylethylene (1). The resulting polymeric dimethylamino‐substituted 1,1‐diphenylalkyllithium was terminated with methanol or reacted with butadiene to form a diblock copolymer, poly(styrene‐b‐butadiene), with the dimethylamino group at the interface between the blocks. α‐Dimethylaminopolystyrene and α‐dimethylaminopoly‐(methyl methacrylate) were synthesized by using the adduct of1withsec‐butyllithium as initiator, α,ω‐Bis(dimethylamino)polystyrene was prepared by using the functionalized initiator and then terminating the resulting dimethylaminopoly‐(styryl)lithium with1. The amine‐functionalized polymers were characterized by end‐group titration, size exclusion chromatography, thin‐layer chromatography, vapor phase osmometry, elemental analysis and both1H and13C NMR spectroscopy. All experimental evidence is consistent with quantitative functionalization

ISSN:0007-1641    

DOI:10.1002/pi.4980230109

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractTelechelic ionomeric elastomers with quaternary ammonium groups (Me2RN+) attached terminally to polybutadiene (M̄n∼ 2.7 × 103; M̄w/M̄n= 1.27; containing 62% 1,4‐linkages) have been synthesised by an anionic technique using a functionalised initiator and terminator, followed by quaternisation of the resulting α,ω‐bis(dimethylamino)polybutadiene. By using differing alkyl halides for quaternisation and by ion exchange chromatography, a series of dialkylated telechelic cationomers has been produced containing alkyl groups, R = Me, Et,n‐Pr,n‐Bu orn‐C5H11with counter anions X = I−, Br−, PF 6−or SO 42−. The glass transition temperatures,Tg, of these cationomers arec.6°C higher than for the precursor, non‐quaternised polymer but are essentially unchanged with variations in groups R or anions X. Dynamic mechanical thermal analyses of the cationomers have been carried out and a secondary transition,Ti, associated with relaxation of ionic cross‐linking interactions, observed. Values ofTidecrease as the size of R increases from C1to C5, and as the anion X is changed from Br−to I−to PF 6−or SO 42−to PF 6−.Activation energies can be derived from the frequency dependence ofTivalues or from the temperature dependence of shift parameters, obtained from the master curves of the dependence on frequency of the shear storage (G') and loss (G') moduli; these activation energies are dependent on the nature of the counter anion, being greatest for the polymer containing the dinegative SO 42−, but are essentially unchanged by the variations in alkyl group, R, implemented in this study. Other results of the dynamic mechanical analyses on the cationomeric elastomers

ISSN:0007-1641    

DOI:10.1002/pi.4980230110

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractAbstract: High intensity ultrasound has been used to prepare homopolymers and copolymers of styrene, methyl methacrylate and n‐butyl methacrylate. High molecular weight homopolymers are formed rapidly during sonication and are then subjected to a degradation process. The copolymers prepared by this method have similar structure and properties to those prepared using AIBN as an initiato

ISSN:0007-1641    

DOI:10.1002/pi.4980230111

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY