Acta Polymerica最新文献

Composites consisting of polymer matrix materials and natural or synthetic layered minerals e.g. clays were prepared by using special compatibilizing agents between these two intrinsically non-miscible components. Block or graft copolymers combining one part of the polymer that is identically and/or completely miscible with the organic polymer and another part that is compatible with the natural mineral are applied to act as compatibilizer. The interaction between the first part of the compatibilizer is preferentially an ionic interaction or an interaction via hydrogen bonds. This interaction leads to a separation of the mineral into single sheets and/or small clusters containing approximately 2–10 sheets and a subsequent homogeneous incorporation of these clusters into the polymer matrix material.

This paper summarizes the work carried out during 3 years in a Network of the program “Human Capital and Mobility” of the European Union CHRX 93-0159 entitled “Reactive surfactants in heterophase polymerization for high performance polymers”. A series of about 25 original papers will be published in the open literature under the general title of this feature article from Part I to Part XXV. The synthesis of selected surfactants either anionic or non ionic, and as well inisurfs (both initiators and surfactants), transurfs (both transfer agent and surfactants) or surfmers (both comonomers and surfactants) is shortly described. They were applied in emulsion polymerization and dispersion polymerization, and their behavior in shortly discussed. Finally films have been produced from a few of them, mainly from surfmer with maleic reactivity, and the main properties, and interests of such films are discussed.

A simple, reproducible, already introduced grafting method of methacrylic monomers onto carbon fibers is applied to cyano-biphenyl containing liquid crystalline (lc) monomers. The development of lc phases is faster and more uniform in the presence of carbon fibers. Applying a voltage to the grafted carbon fibers, causes phase transitions of the liquid crystals. By varying spacer length of the grafted lc polymers the physico-chemical properties, e. g. wetting and electrokinetic behavior (zeta-potential) are significantly influenced.

Extending the considerations of previous work (Acta Polym. 1997, 48, 30; Acta Polym. 1997, 48, 298) the degree of branching (DB) and the average number of branches per non-terminal monomer unit (ANB) are defined and calculated for random copolycondensation of AB_m with AB monomers as well as AB_m with AB_n-monomers in general. Copolymerization of linear AB-comonomers can be used to deliberately lower the DB and ANB of hyperbranched polymers. The DB$�{}_{�\text{AB/AB}�{}_{�\text{2}�}�}$ for copolycondensation of AB and AB₂ monomers in dependence on the monomer ratio r = [AB]/[AB₂] and conversion p_A is DB$�{}_{�\text{AB/AB}�{}_{�\text{2}�}�}$ = 2 p_A r + 1/( r + 2)². The DB$�{}_{�\text{AB/AB}�{}_{�\text{2}�}�}$ for copolymerization is compared to the DB for AB₂ homopolymerization,showing that a relatively small fraction of AB₂ comonomers suffices to obtain considerable degrees of branching. Also, the DB$�{}_{�\text{AB/AB}�{}_{�\text{3}�}�}$ and ANB$�{}_{�\text{AB/AB}�{}_{�\text{3}�}�}$ for copolycondensation of AB and AB₃-monomers are calculated. Finally, a general expression for the DB$�{}_{}$

Several novel side chain liquid crystalline polysiloxanes have been prepared containing a chiral cyanohydrin moiety prepared using enantioselective synthesis. Homopolymers incorporating a side chain with the chiral group exhibited no liquid crystalline behavior. Copolymers of the side chain with the cyanohydrin group with an alkenyloxybenzoate yielded polymers exhibiting a N* phase. Increased amounts of the side chain with the cyanohydrin moiety led to a decrease in the transition temperatures of the resulting copolymers. Dielectric relaxation studies showed that all polymers exhibited δ motion due to relaxation of the longitudinal dipole of the mesogen around its short axis. One copolymer with a large amount of the chiral unit and a long flexible spacer exhibited distinct α and δ relaxations where the α relaxation is assigned to the motions of the dipoles perpendicular to the side chain. The fact that both are clearly seen as independent peaks rather than in a broad peak which must be deconvoluted is indicative of the fact that long, flexible spacer chains decouple the two motions from each other. The δ process for the polymers with a small amount of the cyanohydrin side chain tended to be dominated by the non-chiral pendant group. The motion of the polymer with an increased amount of the pendant group containing the chiral moiety was dominated by the cyanohydrin side chain and the δ relaxation was much slower (longer relaxation time) due to the bulky nature of the chiral moiety.

Electrically conducting poly(thiophenes) functionalized with hexyl and cyclohexyl side chains have been synthesized. Poly[3-hexyl thiophene-co-3-cyclohexyl thiophene] with different hexyl and cyclohexyl contents were synthesized and characterized. The regioregularity of the copolymer was very much affected and the amount of miscouplings rose with the increase of cyclohexyl thiophene. These structural defects affect the optical, conducting and electrochemical properties of the copolymer.

We have recently synthesized a series of poly(3-alkylthiophenes) with a new simple procedure which has allowed to prepare 96–100% regioregular polymers. This work describes this synthetic pathway and reports the characterization of a poly(3-alkylthiophene) series obtained through this method.

In this work, a new adamantane-type cardo dicarboxylic acid containing ether group, 2,2-bis[4-(carboxyphenoxy)phenyl]-adamantane (BCAPA), was prepared from 2,2-bis(4-hydroxyphenyl)adamantane and p-fluorobenzonitrile via the aromatic nucleophilic substitution reaction followed by hydrolysis. A series of new polyamides were prepared by the direct polycondensation of BCAPA and various diamines utilizing Yamazaki reaction conditions. The polymers were produced with moderate to high inherent viscosities of 0.65–1.06 dl g^–1. The polymers, except polymers PA4, PA7 and PA8, exhibited weight-average molecular weight and number-average molecular weight in the range of 57 400–106 000 and 32 500–58 200, respectively. Nearly all the polymers were readily soluble in polar solvents such as N-methyl-2-pyrrolidinone, N,N-dimethylacetamide, and N,N-dimethylformamide, as well as less polar solvents such as dimethyl sulfoxide, pyridine and γ-butyrolactone, and also in tetrahydrofuran. All of the polymers were amorphous and the polyamide films had a tensile strength and tensile modulus above 86 MPa and 2.0 GPa. These polyamides had glass transition temperatures between 254–292°C and 10% weight loss temperatures in the range of 450–507 and 481–516°C in nitrogen and air atmosphere, respectively.

The main focus of this study is the development of new polypropylene macromolecules. The simultaneous supporting of two metallocenes that manufacture polyolefins of different tacticity on the same silica should yield stereoblock polymers of polypropylene, if a chain transfer between the active species takes place. As chain transfer agents two aluminumalkyls (cocatalyst and scavenger) of distinct steric demands were chosen. Two catalyst systems were studied. The first was based on a PQ-silica/MAO on which the two metallocene catalysts rac-Me₂Si[Ind]₂ZrCl₂ (isotactic working species) and i-Pr[FluCp]-ZrCl₂ (syndiotactic working species) were fixed. For the second the components rac-Me₂Si[IndR₂]₂ZrCl₂ and i-Pr[FluCp]-ZrCl₂ were fixed to a Grace Silica/MAO-support. The influence of the type of silica, of MAO-content, of the kind of scavenger and of the supporting procedure on the microstructure, the kinetics and the morphology of the product were investigated.

Tailored diblock copolymers of rigid poly(p-benzamide) (PBA) and flexible poly(ethylene glycol) (PEG) were prepared using two different polymerization schemes: (i) the one-pot two-step scheme of the Yamazaki reaction including benzoyl-terminated PBA and a PEG methyl ether modified by p-aminobenzoylation; (ii) the polymerization of p-aminobenzoic acid in the presence of the above NH₂-terminated PEG. The former method yields a copolymer coexisting with a large amount of PBA homopolymer. The latter method yields a copolymer with a reduced and controlled amount of unblocked PBA. The fraction of flexible segments in the copolymers varied between ca. 0.60 and ca. 0.40. In solutions of N,N-dimethylacetamide/LiCl, the solubility of the flexible homopolymer is larger at low LiCl content when the solubility of rigid PBA is, instead, negligeably small. However, large quantities of the latter are solubilized at low LiCl content, provided the copolymer is also present. The order of increasing solubility of the two components is reversed at high LiCl content. Micellar-type organizations of the amphiphilic copolymer with the rigid homopolymer are postulated. A lyotropic mesophase appears at a copolymer volume fraction v_pⁱ ca. 0.06 and it is fully formed at v_p^a ca. 0.08. The evolution of the structurization from diluted solutions to the mesophase and to the solid state is briefly considered.