摘要:

AbstractPropene polymerizations in the presence of the homogeneous catalytic system Cp2Ti(C6H5)2‐Al(CH3)3‐Al(CH3)2F were performed at different monomer concentrations in CH2Cl2. A relevant increase of the polymerization rate is observed, resulting in polymer productivities higher than those obtained with methylaluminoxane cocatalyst in toluene. The dependence of the monomer conversion on the propene concentration seems to support the hypothesis of a cationic catalytic site. Similar results were obtained with a homogeneous catalyst based on a chiral zirconocene and Al(CH3)3‐Al(C

ISSN:0025-116X    

DOI:10.1002/macp.1989.021901001

出版商:Hüthig&Wepf Verlag    

年代:1989

数据来源: WILEY

摘要:

AbstractThe addition of mercaptoacetic acid upon radical initiation onto carboxytelechelic polybutadienes (1) which have an average mass M̄n= 4400 gives polyacids having about twelve carboxylic groups. The reaction is followed by13C NMR,1H NMR and by GPC. The thiol disappears according to a first order law. Besides, the value of the modification rate obtained from acido‐basic titration confirms that obtained from NMR. In a second step, 2,3‐epoxypropyl methacrylate is added to the acid groups to obtain an insaturated and carboxylated polydienic oligomer5. An application of these oligomers processed with a reactive diluter shows their high cross‐linking ability under UV irradiation and confirms the improvement of the flexibility properties compared to those of traditional insaturated oli

ISSN:0025-116X    

DOI:10.1002/macp.1989.021901002

出版商:Hüthig&Wepf Verlag    

年代:1989

数据来源: WILEY

摘要:

AbstractAn allyl‐terminated polydimethylsiloxane (PDMS) macromonomer was synthesized by anionic polymerization of hexamethylcyclotrisiloxane (D3) initiated by allyllithium. The molecular weight (MW) of the macromonomer was consistent with that calculated from the ratio of the monomer consumed to the amount of the initiator used, and the molecular weight distribution (MWD) of the macromonomer was narrow. Graft copolymers with polyethylene backbone and uniform PDMS grafts, PE‐g‐PDMS, were prepared by copolymerization of the macromonomer with ethylene using VOCl3/Et2AlCl as the catalyst. Under the copolymerization conditions, the scission of SiOSi bonds by the catalyst is negligible, so that MW and MWD of the PDMS grafts could be considered to be the same as those of the original PDMS mac

ISSN:0025-116X    

DOI:10.1002/macp.1989.021901003

出版商:Hüthig&Wepf Verlag    

年代:1989

数据来源: WILEY

摘要:

AbstractMacromonomers6a,b, carrying phosphatidylcholine analogous and azobenzene moieties as a photoresponsive pigment, were prepared from the reaction of 2‐oxo‐1,3,2λ5‐dioxaphospholane derivatives2and poly[2‐dimethylaminoethyl methacrylate] macromonomer5. 6bshows a nematic phase. The mesogenic group is connected with the chromophore via a flexible spacer group. Phase transition temperatures were determined by measurement of the rapid change in conductivity of the solutions of the amphiphiles with the temperature. From the result of photoreversible cis‐trans isomerization it can be concluded that6bcan possibly be used as a photoresponsive material of

ISSN:0025-116X    

DOI:10.1002/macp.1989.021901004

出版商:Hüthig&Wepf Verlag    

年代:1989

数据来源: WILEY

摘要:

AbstractThis work deals with the modification reaction of dextran with 2‐acetoxybenzoyl chloride (acetylsalicyloyl chloride) using tertiary amines as catalyst/acceptor systems and the DMF/LiCl system as solvent. The structure of the resulting polymers was determined by means of IR,1H and13C NMR spectroscopy. Transesterification reactions were observed when 4‐dimethylaminopyridine or pyridine were used as catalysts, with the formation of acetoxy, 2‐hydroxybenzoyloxy (salicyloyloxy) and 2‐acetoxybenzoyloxy (acetylsalicyloxy) groups. When triethylamine was used as catalyst, only acetylsalicyloyloxy groups were found to be grafted onto the polymer chain. A linear dependence of the reaction rate on the concentrations of polymer, acetylsalicyloyl chloride and triethylamine was found. The activation energy was found to be 13,8

ISSN:0025-116X    

DOI:10.1002/macp.1989.021901005

出版商:Hüthig&Wepf Verlag    

年代:1989

数据来源: WILEY

摘要:

AbstractAddition of aluminium compounds to the stable metal‐carbene complex tetracarbonyl[4–5‐η‐1‐methoxy‐4‐pentenylidene]tungsten (1), showing an intramolecular coordination of double bond to the transition metal, leads to highly active catalytic systems in the polymerization of norbornene. It is shown that, in optimal conditions, AlCl3is more efficient than AlEt3for cyclo‐olefin polymerization. From spectroscopic studies (UV‐visible,1H and13C NMR) of the activated system1‐AlCl3, a mechanism of activation by AlCl3is proposed involving a modification of the nature of carbe

ISSN:0025-116X    

DOI:10.1002/macp.1989.021901006

出版商:Hüthig&Wepf Verlag    

年代:1989

数据来源: WILEY

摘要:

AbstractA homopolymer ofL‐lactic acid (LA), which was synthesized by direct polycondensation in the absence of a catalyst at 200°C, is crystalline, in contrast to the homopolymer ofD,L‐mandelic acid (MA) which is amorphous. Poly(LA‐co‐MA), obtained under the above conditions, is amorphous over a wide range of composition from 15 to 100 mol‐% of monomeric units of MA. The in vitro degradation mechanism of these homopolymers shows a parabola‐type degradation pattern for poly(LA) and no degradation throughout an experimental period of 15 weeks for poly(MA). In poly(LA‐co‐MA) the degradation mechanism leads to a typical S‐type degradation pattern, which may be divided into two processes, initial swelling at the surface of the matrix without degradation (induction period), followed by the erosion of oligomers produced by degradation of the main chain in

ISSN:0025-116X    

DOI:10.1002/macp.1989.021901007

出版商:Hüthig&Wepf Verlag    

年代:1989

数据来源: WILEY

摘要:

AbstractGraft copolymers composed of monomeric units of hydrophobic butyl methacrylate and those of the hydrophilic, non‐ionizable macromonomer 2‐(N‐methyl‐N‐4‐vinylphenethylamino)ethylaminopoly[N5‐(2‐hydroxyethyl) or (3‐hydroxypropyl)‐L‐glutamine] (4aor4b) were synthesized. The permeability of phenyl‐1,2‐ethanediol across the membranes prepared from these copolymers was found to be affected by the conformation of the poly[N5‐(ω‐hydroxyalkyl)‐L‐glutamine] branch which depends on its chain length and the hydrophobicity of the solvent

ISSN:0025-116X    

DOI:10.1002/macp.1989.021901008

出版商:Hüthig&Wepf Verlag    

年代:1989

数据来源: WILEY

摘要:

AbstractDetermination of active centres using TiCl4/MgH2‐supported catalyst system in ethylene polymerization is reported. A radio‐tagging technique, whereby14CO is used to label the polymerization active centres, is employed. Optimization of the14CO/Ti ratio showed that the polymer radioactivity remained constant after a14CO/Ti ratio of about 8 was attained. At the optimal14CO/Ti ratio, it is found that up to 14% of the titanium on the catalyst surface are active in polymerizations at 40°C, 10 min reaction time, and 30 min contact time period of14CO with the polymerization medium. Moreover, the value of the corresponding propagation rate constant,Kp, was found to be about 230 dm3/(mo

ISSN:0025-116X    

DOI:10.1002/macp.1989.021901009

出版商:Hüthig&Wepf Verlag    

年代:1989

数据来源: WILEY

摘要:

AbstractTelechelic oligo(dimethylsiloxane)s6and7with chloro‐, cyano‐ or aminopropyl end groups were synthesized from the corresponding chlorodimethylsilanes2a–cand α‐hydro‐ω‐hydroxyoligo(dimethylsiloxane)s4and5. The ω‐cyano derivatives6band7bwere reduced to the 4‐aminobutyl derivatives8aand8bwith LiAlH4.8awas subsequently transformed into 1,7‐bis(4‐maleimidobutyl)‐1,1,3,3,5,5,7,7‐octamethyltetrasiloxane (10) by reaction with maleic anhydride, via the intermediate dimaleamic acid9. The products were characterized by IR,1H,29S

ISSN:0025-116X    

DOI:10.1002/macp.1989.021901010

出版商:Hüthig&Wepf Verlag    

年代:1989

数据来源: WILEY