摘要:

AbstractFour new ω‐ferrocenylalkyl diethyl malonates with varying length of the alkyl group from 4 to 10 methylene units were incorporated via Ti(OiPr)4‐catalyzed copolymerization into smectic liquid crystalline main‐chain polymers in contents of about 10 mol‐%. As mesogenic unit 4,4′‐bis(6‐hydroxyhexyloxy)azoxybenzene was used as diol component and diethyl phenyl malonate as diester component. Polymer analogous oxidation of the ferrocene units leads to liquid crystalline ionomers, which also form smectic phases. The ferrocene containing polymers were investigated in the oxidized and non‐oxidized state of the ferrocene unit. Differential scanning calorimetry (DSC) data show a shift towards higher phase transition temperatures after oxidation, which is in agreement with the behaviour of classical ionomers. Small angle X‐ray scattering (SAXS) experiments show an excess scattering to small angles, which is a hint for dispersed particles in the polymer matrix (ionic clusters). In one polymer series the ferrocene content was varied. Increasing the ferrocene content changes the type of the LC phase from smectic A to nematic presumably because of the bulkiness of the neutral ferrocene group. It is, however, possible to restore the smectic A phase by an oxidation of the ferrocene units to ferrocenium ions. This is a result of microphase separation in ionic domains and non‐ionic domains, which supports the formation o

ISSN:1022-1352    

DOI:10.1002/macp.1997.021981201

出版商:Hüthig&Wepf Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractSeveral kinetic aspects of the polymerization of dodecyl acrylate photoinitiated withp‐nitroaniline in the presence of an aliphatic tertiary amine, either 2‐(N,N‐diethylamino)ethanol or 2‐(N,N‐dimethylamino)ethyl methacrylate, acting as coinitiator, were studied. Under low absorption conditions, the rate of polymerization was found to be proportional to the square‐root of the incident light intensity, the initiator and the coinitiator concentrations. The polymerization behaviour was analyzed also under aerobic conditions. Under identical irradiation conditions, both initiation and polymerization processes present higher rates and quantum yields than those obtained with conventional aromatic ketone phot

ISSN:1022-1352    

DOI:10.1002/macp.1997.021981202

出版商:Hüthig&Wepf Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractRegioselective substituted cellulose phenyl urethanes form lyotropic liquid crystalline mesophases in highly concentrated solutions with certain solvents. The structural and optical properties strongly depend on the site of substitution, e.g., 2‐, 3‐, 6‐position of the glucose residues as well as on the specific substitution of the phenyl ring of the carbamate group by fluorine, chlorine or methyl as compared to hydrogen and on the external parameters as concentration and temperature. By variation of the carbamate side groups a change of the helicoidal twist sense of the cholesteric structure is achieved leading to a compensation of left‐ and right‐handed twists that is to a quasi‐nematic structure. The experimental optical rotatory power can be described following theoretical considerations of de Vries by introducing a dispersion and a d

ISSN:1022-1352    

DOI:10.1002/macp.1997.021981203

出版商:Hüthig&Wepf Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractWell defined ABC triblock copolymers of polystyrene‐block‐poly(2‐vinylpyridine)‐block‐poly(tert‐butyl methacrylate) and polystyrene‐block‐poly(4‐vinylpyridine)‐block‐poly(tert‐butyl methacrylate) were synthesized by sequential living anionic polymerization in tetrahydrofuran. Triblock copolymers with narrow molecular weight distribution were obtained. Hydrolysis of the poly(tert‐butyl methacrylate) block yields polystyrene‐block‐polyvinylpyridine‐block‐poly(methacrylic acid) which demonstrates pH‐dependent solution properties. Interpolymer complexation of the polyvinylpyridine and poly(methacrylic acid) blocks in the micellar solution is studied in dependence of the pH in solution by potentiometric, conductometric and turbidimetric titratio

ISSN:1022-1352    

DOI:10.1002/macp.1997.021981204

出版商:Hüthig&Wepf Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractOligomers of 2,5‐dialkyl‐1,4‐phenylenevinylenes (DR‐OPV, R = C4H9, C7H15, C10H21and C6H11) (CyH) were prepared via metathesis polycondensation of the respective 2,5‐dialkyl‐1,4‐divinylbenzenes. The synthesis of the monomers is described. The highly active metal‐alkylidene complex Mo(NAr Me 2)(CHCMe2Ph)[OCMe(CF3)2]2(Ar Me 2= 2,6‐dimethylphenyl) serves as a catalyst. The degree of polymerization can be controlled by variation of the solvent and by the length of the side chains, since the reaction proceeds as a precipitation polycondensation. The DR‐OPVs are bilious‐green products and, depending on the molecular weight, soluble in various solvents like toluene, THF and CHCl3. The solutions are highly fluorescent and coloured. The DR‐OPVs have vinylic end groups. The vinylene double bonds are of all‐transconfiguration. Due to their rigid‐rod structure, the DR‐OPVs synthesized have a distinct tendency to crystallize in a highly ordered sta

ISSN:1022-1352    

DOI:10.1002/macp.1997.021981205

出版商:Hüthig&Wepf Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractBy means of27Al,1H,17O and13C NMR spectroscopy the structure of the methylaluminoxane (MAO) cocatalyst of Kaminsky‐Sinn catalysts was investigated. We have found that the27Al NMR resonance line of MAO is extremely broad at room temperature (δ ≈ 60, Δω1/250 ± 10 kHz). At elevated temperatures (40–120°C) MAO exhibits an27Al resonance at δ 110 ± 10, Δω1/215–10 kHz, that is, within the range reported for the aluminoxane clusters [(t‐Bu)Al(μ3‐O)]6and [(t‐Bu)Al(μ3‐O)]9with cage structures. The27Al resonance at δ 149–153, usually attributed to MAO, belongs to AlMe3present in MAO samples. The17O NMR resonance of MAO at 50°C (δ 67, Δω1/21.7 kHz) is within the range typical for three‐coordinate oxo ligands, but it can be attributed only to a minor part of MAO oligomers. It was shown that the intensity of27Al and17O NMR resonances of MAO increases with increasing temperature, whereas the width of both resonances is almost constant. The results obtained lead to the conclusion that at ambient conditions MAO forms oligomers (MeAlO)nwith cage structure and MeAlO3environment. Upon increasing the temperature these oligomers reversibly break into smaller MAO units. Based on the27Al NMR data the average radius (R) of MAO oligomers is approximately 5.1 ± 0.3 Å at 120°C. This radius corresponds to (MeAlO)nspecies with 9

ISSN:1022-1352    

DOI:10.1002/macp.1997.021981206

出版商:Hüthig&Wepf Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractThe kinetics of the initiation of isoprene polymerization in heptane with the hydrocarbon‐soluble alkylsodium compound 2‐ethylhexylsodium was studied. Initiation rates were estimated from the induction period and by measuring UV spectra of polyisoprenyl‐sodium (λmax= 304 nm) during the course of polymerization. The initiation reaction is first order in initiator both in the course of the reaction and with respect to the starting concentration of the initiator. The same result is obtained when 2‐ethylhexyllithium is used. The initiation rate constants are:ki= 1,6 · 10−3and 5,5 · 10−4L/(mol · s) for sodium and lithium compounds at 26°C, respectively. Aggregated forms of organoalkali compounds are suggested to take part in the initiation reaction of isopren

ISSN:1022-1352    

DOI:10.1002/macp.1997.021981207

出版商:Hüthig&Wepf Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractTwo poly(2‐vinylpyridine)s fully quaternized with a ω‐(4′‐methoxy‐4‐biphenylyloxy)‐alkyl group (alkyl chain of 9 and 11 carbon atoms) have been synthesized by the well known spontaneous polymerization of vinylpyridinium salts. When heated, these polymers (P2VPC9 and P2VPC11) show thermotropic liquid crystal properties. According to the X‐ray diffraction data, the observed smectic mesophase in both polymers is of the type A (SA). Results are discussed in comparison with other molecular and polymeric pyridinium salts previously described. A molecular arrangement model for the P2VP derivat

ISSN:1022-1352    

DOI:10.1002/macp.1997.021981208

出版商:Hüthig&Wepf Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractThe interaction of cationic surfactants from the series of dimethylbenzylalkylammonium chlorides (DMBAAC, alk. = CnH2n+1(n= 10, 12, 14)) with water‐soluble copolymers ofN‐vinyl‐2‐pyrrolidones (VP) with methacrylic, acrylic, and crotonic acids in aqueous and aqueous‐salt solutions was investigated by polarized luminescence. It was established that the main factors determining the stability of water‐soluble DMBAAC complexes with carboxyl‐containing VP copolymers include the composition and structure of the copolymer, the length of the alkyl group of DMBAAC, the ratio of the interacting components, the pH, and the ionic strength of the solution. The equilibrium dissociation constants of these complexes in aqueous solution were determined. Potentiometric titration, turbidimetry, and viscometry showed that the complexation features manifested by the interaction of individual DMBAAC's with carboxyl‐containing VP copolymers are also characteristic of complexation processes occurring with participation of industrial DMBAAC, which is a mixture of indi

ISSN:1022-1352    

DOI:10.1002/macp.1997.021981209

出版商:Hüthig&Wepf Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractUsing the Mayo and the Clay‐Gilbert method, the transfer rate coefficient of α‐thioglycerol (TG) was determined at 50°C for the polymerization of methyl methacrylate (MMA) in a 3 mol · L−1tetrahydrofuran solution using different amounts of 2,2′‐azoisobutyronitrile (AIBN) as initiator. The transfer rate coefficient was found to be independent of the initiator concentration and higher by a factor of 1.6 when obtained according to the Clay‐Gilbert method compared to t

ISSN:1022-1352    

DOI:10.1002/macp.1997.021981210

出版商:Hüthig&Wepf Verlag    

年代:1997

数据来源: WILEY