摘要:

AbstractThe application of stopped‐flow FT‐IR spectroscopy to group transfer polymerization (GTP) and cyclic oligomeric carbonate formation is described. The influence of catalyst structure, propagating end stereochemistry and degree of polymerization (DP) on the rate of monomer addition was examined for GTP. Also, the major GTP termination process was identified and characterized. Model reactions were used to study the kinetics of acyl ammonium salt formation and subsequent conversion to urethane. These results were used to further develop the mechanism of bisphenol A‐bischloroformate macrocycliz

ISSN:0025-116X    

DOI:10.1002/macp.1993.021940501

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractThe η3, η2, η2‐dodeca‐2(E), 6(E), 10(Z)‐trien‐1‐yl‐nickel(II) complexes [Ni(C12H19)]X (X = SbF6, O3SCF3) were treated in toluene with amorphous aluminium trifluoride (which was prepared from AlEt3and BF3· OEt2) in a mole ratio 1 : 10 to 20, forming a highly active catalyst for the 1,4‐cispolymerization of butadiene. This catalyst is comparable in its activity and selectivity, and in the molar mass distribution of the polybutadiene, with the technical nickel catalyst Ni(O2CR)2/BF3ċOEt2/AlE3developed by Bridgestone Tire Company thirty years ago. The existence of the C12‐allynickel(II) cation [Ni(C12H19)]+on the AlF3support could be proved by FAB mass spectroscopic measurements. In agreement with our reaction model for the allyl nickel complex catalyzed butadiene polymerization, it is concluded that the technical nickel catalyst in its effective structure can be described as a polybutadienylnickel(II) complex co‐ordinated to a polymeric fluoroaluminate anion

ISSN:0025-116X    

DOI:10.1002/macp.1993.021940502

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractFormation of a banded texture was observed in thin films of a polydiacetylene prepared from the lyotropic nematic phase subject to flow. The banded texture was experimentally investigated by polarizing light microscopy and transmission electron microscopy. The banded structure is initially formed in a nematic phase of the polymer and could be imaged by TEM after its transformation to a lamellar phase which is the polymer analogon to a smectic phase in low‐molecular‐weight compounds. A mathematical description of the texture is given. During further relaxation of the system in the lyotropic state the initial orientation is lost by the formation of disclinati

ISSN:0025-116X    

DOI:10.1002/macp.1993.021940503

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractThe homopolymer of trimethylolpropane triacrylate (TMPA) was synthesized by suspension polymerization using a thermodynamically good solvent (toluene) as a porogen (vol. ratio 1:1). This polymer possesses a high specific surface area (437 m2· g−1) and porosity (50%). It was found by sorption of benzene and cyclohexane that the majority of the pores are in the range of 1–5 nm. Sorption of phenol, a standard sorbate, from a water solution is proportional to the specific surface area of the mesopores. This sorption is higher than that of nonspecific sorbents (like styrene/divinylbenzene copolymers) and smaller than the sorption of specific ones (like acrylonitrile/divinylbenzene copolymers).Two sets of reactive copolymers were obtained. In the first set, TMPA (20–40 vol.‐%) was polymerized with acrylonitrile (AN) in the presence of a constant amount of toluene as an inert diluent (vol. ratio 1:1). In the second set of copolymers the cross‐linking degree was kept constant (30 or 40 vol.‐% of TMPA) but various solvent mixtures were used, namely: toluene/tetradecane or hexadecane, toluene/2‐ethylhexanol, cyclohexanol/tetradecane or hexadecane, cyclohexanol/2‐ethylhexanol (vol. ratio 9:1). It was found that all the copolymers are macroporous (volume of pores approx. 1,0 cm3· g−1) but those obtained in the presence of good solvents display a higher specific surface area and hence better sorption properties towards phenol than those obtained in the presence of poor solvents. The swelling of AN/TMPA copolymers is smaller than that of the TMPA homopolymer due to the presence of additional physical crosslinks formed by the strongly p

ISSN:0025-116X    

DOI:10.1002/macp.1993.021940504

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractOxidation of poly(vinyl alcohol) (PVA) with 1‐oxo‐4‐methoxy‐2,2,6,6‐tetramethylpiperidinium chloride (oxoammonium salt,1) prepared by a one‐electron oxidation of the corresponding nitroxyl radical (2) was carried out. PVA with a degree of polymerization (DP) of 300 and a degree of saponification (DS) of 88 mol‐% was oxidized with1in the presence of magnesium perchlorate inN‐methyl‐2‐pyrrolidone (NMP) to obtain a polymer containing 66 mol‐% of ketone units. The oxidation was found to be dependent on solvent and additive and further, independent of DP but dependent on DS of PVA. In the case of PVA with extremely low (10 mol‐%) or high (98,5 mol‐%) DS, no or little oxidation took place. The highest ketone content was obtained in a polymer with a DS of 88 mol‐%. Moreover, the ketone content of the oxidized PVA could be c

ISSN:0025-116X    

DOI:10.1002/macp.1993.021940505

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractThe phase equilibrium of plasticized polymer systems on the basis of cellulose diacetate and ethylene glycol esters of dibasic aliphatic acids (from oxalic acid to 1,10‐decanedicarboxylic acid) was studied and the solubility parameters and the thermodynamic interaction parameters of the components were calculated. It is shown that an increase in molecular weight of the plasticizers leads to a lower miscibility of the components, a fact which is reflected in a regular rise of the upper critical solution temperature (UCST), a tendency of the systems for gelation, a decrease of the solubility parameter of the plasticizer δ1, and a growth of the interaction parameters χHand χ12. The results are discussed in terms of the existing theories for polymer solut

ISSN:0025-116X    

DOI:10.1002/macp.1993.021940506

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractMonomers containing several octadecyl groups, e.g., 2‐isopropenyl‐4,6‐bis(octadecylamino)‐1,3,5‐triazine (2), 2‐dioctadecylamino‐4‐isopropenyl‐6‐octadecylamino‐1,3,5‐triazine (3) and 2,4‐bis(dioctadecylamino)‐6‐isopropenly‐1,3,5‐triazine (4) were prepared by the alkylation reaction of 2,4‐diamino‐6‐isopropenyl‐1,3,5‐triazine (1) with 1‐bromooctadecane in the presence of sodium hydride. In the free‐radical homopolymerization of these monomers, the polymer yield of3was lower than that of2due to a decrease in the ceiling temperature, and the polymerization of4did not proceed. Copolymerizations of these monomers with styrene or methyl methacrylate were carried out and the monomer reactivity ratios (r1andr2) were determined. The monomer reactivity decreased with increasing the number of octadecyl groups in the monomers. Crystallinity of the octadecyl side chains in the resulting comb‐like polymers w

ISSN:0025-116X    

DOI:10.1002/macp.1993.021940507

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractIn this contribution, the X‐ray diffraction (XRD) pattern of a highly oriented sample of syndiotactic polystyrene in the mesomorphic form, collected by an automatic diffractometer, is presented, thus providing quantitative and more complete information relative to the diffracted intensity. The structural changes induced by annealing procedures in mesomorphic samples are shown through the analysis of the XRD patterns: both unoriented and oriented mesomorphic samples are transformed gradually into α‐form crystals. On the basis of these evidences and of preliminary comparisons between the calculated Fourier transform of simplified models and the experimental diffraction intensity, it is suggested that the local organization in triplets oftrans‐planar chains, typical of the different modifications of the α‐form, would be largely present also in the disordered chain agglomerates of the mesomor

ISSN:0025-116X    

DOI:10.1002/macp.1993.021940508

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractHeparin was bonded covalently to hydrophilic polyurethanes. Polymers were characterized by spectroscopic techniques (IR and1H,13C NMR), molecular weight measurements and differential scanning calorimetry. The heparin content of the polymer films (up to more than 500 μg/cm2) was determined by a calorimetric system, and its biological activity was evaluated in vitro by APTT (activated partial thromboplastin time) measurements with a tenfold increase of the clotting time (about 300 s) with respect to the clotting time of human plasma (30 s). When heparin is bonded to a polymer provided with a hydrophilic polyfunctional spacer, the heparin content of the films is remarkably higher than previously described (about twice the reported values), and also the biological activity of the bonded heparin is favourably affected

ISSN:0025-116X    

DOI:10.1002/macp.1993.021940509

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractThe composition and sequence distribution of copolymers of maleic anhydride (MA) withp‐methoxystyrene (p‐MST) andp‐chlorostyrene (p‐CST) prepared in ethyl methyl ketone at 50 ± 0,1°C were analysed using13C DEPT NMR techniques, in order to compare the applicability of composition and sequence distribution data to the study of the mechanism of copolymerisation using the terminal, penultimate and complex‐participation models. In the case of the strongly alternating copolymerisation ofp‐MST with MA, the comparison of models on the basis of sequence distribution data was found to be better at separating each model in terms of its applicability, with the complex‐participation model providing the best fit to the data. In the case of the less strongly alternating copolymerisation ofp‐CST with MA, neither method of comparison could clearly distinguish between the penultimate and complex‐p

ISSN:0025-116X    

DOI:10.1002/macp.1993.021940510

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY