Acta Polymerica最新文献

Three series of polystyrene latices were synthesized using the stepwise seeded emulsion polymerization technique. For kinetic studies reaction was monitored by means of an isoperibolic calorimeter, and synthesized particles were analyzed by means of flow field-flow fractionation combined with multi-angle laser light scattering and by means of rotational disc centrifugation. Latices were found to be in the range from 77 to 442 nm diameter for the first series and from 53 to 210 nm for the second series. The third series were two mixtures of two latices with diameters of 136 and 204 nm respectively 157 and 232 nm. Particle growth between each step is of the factor 1.244 (first series) respectively 1.212 (second series) and therefore slower than theoretically expected (1.26). The particle size distribution width decreases in relative values as particle size increases.

New segmented polyurethanes (SPUs) grafted phospholipid analogous vinyl monomers and polyfunctional monomers were synthesized. The soft segments used in this study were poly(butadiene). The hard segments of these polyurethanes were 4,4′-methylenediphenyl diisocyanate and 1,4-butanediol. The blood compatibilities of the new polymers were evaluated by platelet rich plasma (PRP) contact studies and viewed by scanning electron microscopy (SEM) using medical grade BioSpan and non-phospholipid polyurethane as a reference. The clotting times of the materials in contact with platelet poor plasma (PPP) were also measured. These results of two evaluations suggest that these grafted polymers may be regarded as hopeful biomaterials.

Particles with a copolymer soft core of poly(n-butyl acrylate)/poly(methyl methacrylate) (PBA/PMMA) and a homopolymer hard shell of PMMA were characterized using transmission electron microscopy and solid-state NMR spectroscopy. Two synthesis parameters were investigated: (1) the phase ratio of the core and the shell and (2) the compatibility of the two phases. A series of core-to-shell ratios from 100/0 to 25/75 were synthesized and characterized. The compatibility between the phases was changed (1) by using acrylic acid in either the core and the shell or in both, (2) by synthesizing a homopolymer or a copolymer core or (3) by introducing crosslinking points in the core. The combination of transmission electron microscopy and solid-state NMR spectroscopy allows quantitative determination of the extent of coverage of the core by the shell polymer and the interphase thickness; both were found to depend on the shell content and the compatibility of the phases.

Two monomers, 1,4-bis(4-pyridyl) and 1,4-bis(3-pyridyl) azines were synthesized and characterized. Model pyridinium salts were synthesized by condensation of azines with some bromoalkanes. Polymerization of azines with some dibromoalkanes was also carried out to form pyridinium salt polymers. The structures of both model compounds and polymers were verified from their elemental analysis, IR and ¹H NMR spectra. The liquid crystalline properties of models and polymers were studied by differential scanning calorimetry (DSC) and hot-stage polarizing microscopy. These studies revealed that some synthesized model compounds and polymers exhibit nematic liquid crystal texture having low thermal liquid crystalline stability. The terminal alkyl chains were found to produce mild effect of lowering the transition temperatures. Viscosity measurements indicate that the synthesized polymers have low molecular weight.

Poly[1,4-bis(4-alkyl-2-thienyl)-2,5-disubstituted phenylene]s and their monomers have been regioselectively synthesized in high yield. The head-to-head defined structures of all polymers and monomers are demonstrated by FT-IR, ¹H, ¹³C NMR and elemental analysis. All new materials exhibit good thermally stability, optical, electrochemical properties. Their HOMO and LUMO energy levels are determined by cyclic voltammetry and UV-vis measurement. The improvement of absolute PL quantum yields of all six polymers in the solid films have been approved after the aromatic groups were introduced into the main chain of polythiophene. Three materials were chosen to be fabricated as single layer LED devices.

Polysulfone membranes were modified with acrylic acid using plasma initiated graft polymerization (both in solution and vapor phase) and plasma polymerization. Changes on the surface were monitored by contact angle measurements and FTIR-ATR technique. Pore size and ultrafiltration properties were also evaluated. Grafting in solution gave as a result hydrophobic membranes with pore size diameter signficantly reduced. Such membranes lost their ultrafiltration properties. Grafting in vapor phase seems to give brush-like structure. Membranes possess hydrophilic surface and unique filtration properties in basic environment. Plasma polymerization of acrylic acid on the PSU surface creates a layer of material highly reminding pure poly(acrylic acid). Performance of such membranes was also pH-dependent showing better properties in basic solution.

New Eosin and Rose Bengal ester with an O-benzoyl-α-oxooxime group were synthesized and evaluated as visible light photoinitiators for polymerization in the presence of an amine. The dyes EO-AO and RB-AO are clearly better photoinitiators, with higher Rp values, than the corresponding physical mixtures dye/acyloxime, or than the corresponding pure dyes. However, the relative efficiencies of the different dye/amine and dye/amine/AO mixtures show that if RB is better than EO in the binary mixture, the situation was reversed after addition of AO. The spectroscopic and electrochemical properties of the dyes were measured and the forecasts of thermodynamic calculations were confirmed by time resolved laser spectroscopy experiments which show that the species formed by reaction of the excited dyes eosin and RB with AO were not the same. One observes the dominating formation of the oxidized form of the acyloxime with eosin and its reduced form in the case of Rose Bengal which lead in the case of EO to a larger amount of radicals per photon absorbed and a better initiating efficiency.