J. Labský

The effect of polymeric porogen on the properties of macroporous poly(glycidyl methacrylate-co-ethylene dimethacrylate)

Abstract Macroporous copolymers of glycidyl methacrylate with ethylene dimethacrylate [poly(GMA-co-EDMA)] were prepared using poly(methyl methacrylate) and polystyrene of various molecular weights as a porogen, either pure or in toluene solution. The polymeric porogen remains partly incorporated in the polymer beads. The effect of the polymeric porogen on the shape and size of the particles, porous structure and particle morphology has been studied. The fraction of the oxirane groups accessible to chemical reaction with variously bulky substrates was determined in the particles. Accessibility of the oxirane groups was characterized by the e.p.r. spin-label technique. Quaternary ammonium derivatives of poly(GMA-co-EDMA) exhibited high catalytic activity in nucleophilic substitution.

Small-angle scattering from polyelectrolyte solutions: Dimensions of poly(methacrylic acid) chains in salt-free solutions

Abstract The single-particle scattering function and the radius of gyration of the poly(methacrylic acid) (PMA) molecule have been obtained as a function of the degree of neutralization. A comparison of perturbed and unperturbed dimensions indicates that the expansion of PMA can be ascribed to the presence of charges alone. At a low degree of neutralization ( β ≲0.2), only long-range interactions contribute to the expansion. At higher β values, both long-range and short-range interactions are operative.

Aminolyses of reactive monomers and polymers—I. 4-nitrophenol esters

Abstract A series of 4-nitrophenol esters of N-methacryloylated ω-amino acids were prepared and copolymerized with methyl methacrylate and N-(2-hydroxypropyl) methacryl amide. The rates of aminolyses of monomers and copolymers were compared.

The photochromism of spiropyrans bound on side-chains of soluble polymers

Abstract The effect was investigated of the distance of the photochromic centre of 5′-aminomethyl-1′,3′,3′-trimethyl-6-nitrospiro[2H-1-benzopyran-2,2′-indoline] from the methyl methacrylate chain on the kinetics of the discolouration process. The centre was bound through an amide bond on side-chains consisting of various numbers of methylene groups of ω-amino acids. The thermal discolouration of acetone solutions followed first-order kinetics. Elongation of the side-chain on which the spiropyran unit was bound caused an increase in the thermal discolouration rate. In nonpolar solutions, an effect of polar centres of the polymer chain was superimposed on the dependence.

E.p.r. study of spin-labelled glycidyl methacrylate-ethylene dimethacrylate and styrene-divinylbenzene suspension copolymers in the swollen state

Abstract Reactive groups of homogeneous or macroporous copolymers glycidyl methacrylate-ethylene dimethacrylate and styrene-divinylbenzene containing different amounts of crosslinking agents have been modified in the reaction with an amino derivative of stable nitroxide. The spin-labelled copolymers thus formed were swollen in thermodynamically good or bad solvents and studied by the electron paramagnetic resonance (e.p.r.) method. Two types of spin labels were found in the majority of these copolymers at suitable temperatures and their concentrations were determined. According to our interpretation, the spin labels subjected to rapid rotational diffusion belong to the modified groups localized on chains attached to the inner surface of macroporous copolymers while the spin labels subjected to the very slow rotational diffusion belong to the modified groups localized inside highly crosslinked globules forming the inner structure of the macroporous copolymers. In the less highly crosslinked homogeneous copolymers the modified groups carrying the spin labels subjected to very slow and rapid rotational diffusion are localized in, respectively, the more crosslinked and less crosslinked domains of the polymer beads.

Preparation and properties of polypyromellitimides prepared from 1,n-bis(4-aminophenoxy)alkanes

Abstract Polyamic acids, polyimides and polyisoimides have been prepared from pyromellitic acid dianhydride and 1,n-bis(4-aminophenoxyalkanes). The synthesized polymers were characterized by physical and physico-chemical methods. The prepared polyimides and polyisoimides were found to be insoluble in common solvents and can only be dissolved in sulphuric acid. Compared with highly aromatic polyimides, their thermal stability is lower by 120–140°.

Dynamic behaviour of poly(methacrylic acid) in methanolic solutions

Abstract Methanolic solutions of poly(methacrylic acid) adjusted to various degrees of neutralization with lithium methoxide were investigated by photon correlation spectroscopy. The results obtained are compared with the dynamic behaviour of aqueous solutions. The influence of the solvent dielectric permittivity e on the polyelectrolyte dynamics is discussed (e = 31.4 and 78.5 for methanol and water, respectively). While two diffusive modes corresponding to the dynamics of individual chains and of multi-chain domains can be observed in aqueous solutions, no domains are present in methanolic solutions. The only observable mode (Nernst-Hartley coupled diffusion of polyions and counterions) depends anomalously on the degree of neutralization, indicating the existence of ‘excess counterion counterion condensation’. Both phenomena cannot be explained by the classical polyelectrolyte theory, which takes into account only the change of the dielectric permittivity. The role of counterions in these effects is stressed. They influence the solvent quality and cause a chain collapse reflected in excess counterion condensation. The absence of domains in methanol is ascribed to the relatively low osmotic activity of counterions.

An e.p.r. study of the effect of suspension polymerization conditions on the properties of glycidyl methacrylate-ethylene dimethacrylate particles

Abstract Glycidyl methacrylate-ethylene dimethacrylate (GMA-EDMA) copolymer particles were synthesized by both conventional suspension polymerization and a two-step swelling technique. Oxirane groups in the products were modified by reaction with a mixture of 2,2,6,6-tetramethyl-4-aminopiperidine and its 1-oxyl paramagnetic derivative. The characteristics of the synthesized copolymer particles and the modified oxirane groups were studied with respect to the type of synthesis and the type and content of diluent.

Small-angle scattering by polyelectrolyte solutions: Intermolecular correlation function of poly(methacrylic acid) in salt-free semidilute solutions

Abstract Intermolecular correlations in salt-free solutions of poly(methacrylic acid) neutralized by NaOD were investigated as a function of the degree of neutralization, α. At α = 0, the relative concentration of monomer units belonging to foreign macromolecules at a distance r from a reference monomer unit, g(r) = N(r) N , is nearly equal to unity in the r range investigated. Already at α = 0.01, however, the values of g ( r ) are significantly smaller than unity near the origin. With increasing r , g ( r ) monotonically increases and reaches unity at r = 120–150 A . No oscillations indicating an ordered structure are observed. The shape of g ( r ) curves is in agreement with the correlation hole concept. The non-monotonic dependence of the radius of the correlation hole on α is explained by the overlap of macroions at higher degrees of neutralization.

Effect of spacer on the isomerization of bound azobenzene in soluble polymers

SummaryTwo polymerizable derivatives of 4-aminoazobenzene, viz., 4-methacryloylaminoazobenzene (MA-AAB) and 4-(12-methacryloylaminododecanoyl) aminoazobenzene (MA-12-AAB) were prepared and copolymerized with methacrylic acid (MA) and N-(2-hydroxypropyl) methacrylamide (HPMA). The cis-trans thermal isomerization of these copolymers was investigated as a function of temperature, side chain length and character of the polymer carrier.