摘要:

AbstractThe synthesis of side‐chain liquid crystalline copolysiloxanes containing ω‐[4‐[4‐[(S)‐2‐methylbutoxy]phenoxycarbonyl]‐2‐chlorophenoxy]alkyl side groups is presented. Differential scanning calorimetry, optical polarizing microscopy and X‐ray diffractometry reveal smectic mesomorphism for most of the obtained polymers. The copolysiloxane with three methylene units in the spacer is the only one showing no mesomorphic property. The other four copolysiloxanes, containing four, five, six or eleven methylene units in the spacer, display a smectic A phase. All of the obtained polymers present dual glass transition behavior by both DSC and thermally stimulated current (TSC) techniques. The first glass transition (Tg1) at lower temperature is due to the segmental motions of the polysiloxane backbone, while the second glass transition (Tg2) is due to the cooperative relaxation motions of spacers a

ISSN:1022-1352    

DOI:10.1002/macp.1997.021981001

出版商:Hüthig&Wepf Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractThe cationic polymerization of cyclopentadiene (CPD) in the presence of silica gel particles is initiated by triphenylmethyl chloride, triphenylmethyl bromide, and methyl triflate in 1,2‐dichloroethane. The suspension polymerization yields soluble colourless polycyclopentadiene (PCPD) and intensively blue coloured silica particles (PCPD+silica). The formation of the polymer structure on the silica surface in suspension is followed by transmission UV/VIS spectroscopy and solution (1H and13C) NMR spectroscopy. The structure of the novel solid materials (PCPD modified silica particles) is additionally investigated by DRIFT spectroscopy, solid‐state13C CP/MAS NMR spectroscopy and scanning electron microscopy (SEM).The blue colour of the PCPD+silica particles is caused by polyenylium sequences with five or six conjugated double bonds along the isomerized PCPD chains. The PCPD+structures are compared with similar ionic model compounds derived from retinol and retinal, respectively. The remaining of the PCPD layer including the conjugated sequences on the surface is attributed to the formation of covalent SiOC bonds. Model reactions of the cationically active PCPD+silica particles with benzyltriethylammonium chloride and hexachloroantimonate, as well as charge transfer complex formation of the PCPD polymer layer with carbenium salts, (C6H5)3C+AsF 6−and C7H 7+BF 4−, are also investigated. A possible mechanism for the formation of crosslinked PCPD layers on the silica sur

ISSN:1022-1352    

DOI:10.1002/macp.1997.021981002

出版商:Hüthig&Wepf Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractThe phase diagram of a monodisperse high molecular weight polystyrene (Mw= 3.3 · 106,Mw/Mn<1.06) solution in cyclohexane was thoroughly studied by means of light scattering, cloud point, coexisting phases volume ratio, coexisting phases composition and scanning calorimetry methods, and binodal and spinodal curves were obtained. Coordinates of the UCST (T= 306.2 K, ϕ2= 1.88 · 10−2) determined by different methods were similar. It was found that the first‐order phase transition curve obtained by calorimetric scanning at 10−6K/s accurately fits the spinodal of the system within the concentration range of semidilute and concentrated solutions and has a horizontal part in dilute solutions where the temperature of phase transition was found to be 303.86 K, independently of concentration. At the same temperature a deflection point was found on the concentrated branch of the spinodal. The results were taken as calorimetric evidence of a coil‐globule phase transition in the polystyrene solution. It was shown that the collapse of the polystyrene coils takes place in the metastable system between the binodal and the spinodal in the same way as in the homogeneous solution above t

ISSN:1022-1352    

DOI:10.1002/macp.1997.021981003

出版商:Hüthig&Wepf Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractThe polymerization of styrene initiated by potassium peroxodisulfate was conducted at 50°C in oil‐in‐water microemulsions using sodium lauryl sulfate and 1‐pentanol as emulsifier and cosurfactant, respectively. Based on the experimental findings that both particle size and molecular weight of the polymers are almost independent of styrene conversion and the initial initiator concentration, a kinetic scheme of the microemulsion polymerization of styrene is proposed, which assumes that (1) particle nucleation occurs in monomer‐swollen micelles and almost all the radicals in the water phase enter the monomer‐swollen micelles and finally initiate polymerization therein, (2) with negligible radical termination in the water phase and (3) with negligible radical entry into the preformed polymer particles, and accordingly, (4) all chain‐stopping events in the active polymer particles are chain transfer reactions to monomer. Based on this kinetic scheme, a simple kinetic model is proposed, which can explain fairly well the progress of styrene microemulsion polymerization in the i

ISSN:1022-1352    

DOI:10.1002/macp.1997.021981004

出版商:Hüthig&Wepf Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractA novel molybdenum oxytetrachloride (MoOCl4)‐based ternary catalyst, molybdenum oxytetrachloride/diethylzinc/ethanol (MoOCl4Et2ZnEtOH), induces the living polymerization ofo‐(trifluoromethyl)phenylacetylene. A catalyst composition of MoOCl4:Et2Zn: EtOH (mole ratio = 1:1:3) and anisole as polymerization solvent are favorable. The ratio of weight‐ to number‐average molecular weightsMw/Mnof the polymer was as small as 1,03, and the initiator efficiency was 8%. Living polymerization was verified by multistage polymerization. The polymerization proceeded in a living fashion in the temperature range from 0 to 30°C. The catalyst yielded polymers with smallMw/Mnvalues also from other phenylacetylenes with bulky ortho substituents and 1‐c

ISSN:1022-1352    

DOI:10.1002/macp.1997.021981005

出版商:Hüthig&Wepf Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractThis paper reports on the synthesis and characterization of polyurethane networks based on an α,ω‐dihydroxytelechelic poly(2‐chloroethyl vinyl ether) (PCEVE precursor, type I) and on PCEVE with 2‐hydroxyethyl groups statistically distributed along the chains (PCEVE precursor, type II). The different hydroxyl‐functional polymer precursors were synthesized via “living” cationic polymerization of CEVE to allow the control of molecular weights, molecular weight distributions, as well as, for the dihydroxytelechelic precursor, the chain end functionality. PCEVE precursors of type II were obtained by derivatization of a small fraction of 2‐chloroethyl side groups into 2‐hydroxyethyl groups, using polymer analogous reactions.The mechanical properties of the corresponding PCEVE‐polyurethane (PU) networks were investigated. Data are analyzed in terms of precursor structure and average chain length between crosslinks. The mechanical properties of the PCEVE‐PU networks are also compared to those of PU networks based on hydroxyl‐terminated polybutadiene (HTPB) prepared according to the same experimental procedure. It was found that the networks based on PCEVE have higher toughness to break and highe

ISSN:1022-1352    

DOI:10.1002/macp.1997.021981006

出版商:Hüthig&Wepf Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractA novel coumarin‐containing monomer 6‐[4‐acetoxyphenyl]coumarin‐3‐carboxylic acid (5) was prepared and characterized. It was copolymerized by high‐temperature polycondensation withm‐acetoxybenzoic acid (11) to give copolymers withMnof 5 300–18 000, soluble in common organic solvents and containing up to 40 mol‐% of monomer5. All copolymers were amorphous, withTgincreasing with monomer5ratio (from 147 to 162°C) and high optical quality films preparable by solution casting from chloroform. All polymers show strong photoemission in the blue‐green region and some of them present

ISSN:1022-1352    

DOI:10.1002/macp.1997.021981007

出版商:Hüthig&Wepf Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractFunctional esters of trifluoromethanesulfonic acid (triflate esters) have been synthesized by reaction of functional alcohols (allyl alcohol, 2‐hydroxyethyl acrylate (HEA) and methacrylate (HEMA), 4‐hydroxybutyl acrylate (HBA)) with triflic anhydride in the presence of 2,6‐di‐tert‐butylpyridine. These esters were usedin situas initiators for the polymerization of tetrahydrofuran (THF), with the purpose to synthesize endgroup‐functionalized polyTHF's. The method was first tested with the system butanol/triflic anhydride. With this combination, quantitative formation of the ester and, subsequently, controlled polymerization of THF was realized. Similar results were obtained with the system allyl alcohol/triflic anhydride. With 2‐hydroxyethyl acrylate (HEA) and 2‐hydroxyethyl methacrylate (HEMA), the synthesis of the triflate ester was accompanied by the formation of substantial amounts of ether formed by reaction of the triflate ester with a second molecule of alcohol. This was attributed to an enhanced reactivity of the triflate ester due to nucleophilic assistance by the carbonyl group in γ‐position. This assistance is not possible with 4‐hydroxybutyl acrylate (HBA) and with this alcohol, the formation of the ester was almost quantitative. The synthesis of polyTHF acrylate macromonomer was successful wi

ISSN:1022-1352    

DOI:10.1002/macp.1997.021981008

出版商:Hüthig&Wepf Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractN,N‐Diallyl‐2‐(methoxycarbonyl)allylamine (1a), a trifunctional compound with functional groups of low homopolymerizability, was synthesized and its radical cyclopolymerizability was investigated. Monomer1awas polymerized to yield high molecular weight polymers with a considerably high polymerization rate; the degree of cyclization (DC) of poly(1a) was about 55%, irrespective of the polymerization conditions, while bifunctional compounds with functional groups of low homopolymerizability have been known to yield highly cyclized polymers. Pendant unsaturations detected in poly(1a) were found to consist almost exclusively of allyl groups. The acryloyl groups and one of the allyl groups of1acan be regarded as one functional group in a pair with high polymerizability, sinceN‐allyl‐N‐propyl‐2‐(methoxycarbonyl)allylamine which has the structure of1awith one of its allyl groups saturated has been known to yield linear polymers with a DC of 100%. This consideration indicates that1ahas similar cyclopolymerizability to unsymmetrical bifunctional monomers the functional groups of which have high and low homopolymerizability. This is the reason why1ahas low cyclopolymerizability, since such unsymmetrical bifunctional monomers have generally low cyclopolymerizability. The high polymerization tendency of1ais attributed to the high conjugative nature of the acryloyl group as p

ISSN:1022-1352    

DOI:10.1002/macp.1997.021981009

出版商:Hüthig&Wepf Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractA modified benzyloxycarbonyl (BOC) protective group, the 3,5‐di‐tert‐butyl substituted BOC (3,5‐tBBOC) group, was introduced to the stepwise synthesis of molecularly uniform oligourethanes based on 1,5‐naphthalene diisocyanate (NDI) and 1,4‐butanediol (BDO) for the protection of the amino functions of the starting material 1,5‐naphthalene‐diamine (NDA). Thetert‐butyl substituents of the 3,5‐tBBOC group significantly improved the solubility of the intermediate products in the oligourethane synthesis. Thus, applying this modified protective group, reactions could be carried out, which were not possible with the conventional BOC group, due to the insolubility of the compounds in all suitable solvents. Furthermore, the substituted BOC protective group considerably improved the efficiency of the liquid chromatographical purification of key intermediates of

ISSN:1022-1352    

DOI:10.1002/macp.1997.021981010

出版商:Hüthig&Wepf Verlag    

年代:1997

数据来源: WILEY