N.A. Plate

Kinetic features of the radical polymerization of n-alkylmethacrylates

Abstract The data in the literature and those of the present authors relating to the elementary constants for chain propagation and termination in the radical polymerization of the n-alkylmethacrylate series from methyl methacrylate to cetylmethacrylate are discussed. It is shown that for these monomers, which form comb-like macromolecules the rate constant for chain propagation in bulk remains nearly constant where there is (approximately 300) regular decrease in the rate constant for termination, the decrease being proportional to the number of carbon atoms in the aliphatic ester group. An explanation for this phenomenon is proposed, connected with the difficulty of segmental diffusion of the macroradicals because of interactions of the alkyl groups, this interaction being very characteristics of comb-like polymers. An experimentally based hypothesis is put forward that explains the observed values of the kinetic orders of the reactions with respect to the monomer, which are greater than unity, in terms of the fact that the constant for chain termination changes during polymerization in solution.

Ferroelectric liquid crystalline polymethacrylates

Abstract A new approach to the synthesis of ferroelectric polymers is proposed, based on the appearance of spontaneous electric polarization in the chiral smectic phase C of liquid crystalline polymers. Synthesis, phase transitions, structure, and ferroelectric properties are described for the first representatives of such polymers.

Relaxational transitions and the structure of poly-N-n-octadecylacrylamide☆

Abstract The variation in dielectric relaxation, refractive index, IR absorption and thermomechanical behaviour of poly-N-n-octadecylacrylamide, is studied in the temperature range of −170° to +160°. Transitions have been detected in the region of melting of the side chains of the polymer, close to the glass temperature and in the high elastic state. A molecular interpretation of these processes is proposed.

Investigation of the dielectric polarization of gels of certain comb-like polymers

Abstract The dielectric polarization and dipole moments of gels formed by comb-like polymers have been investigated. It is shown that the macroscopic formation of a gel is proceeded by a conformational transition at the intramolecular level in the solution, which depends on the structure of the solvent and the polymer. It is shown that the degree of defectiveness of the supermolecular structure of the gel is also determined by the chemical nature of the polymer and the solvent.

Comb-like liquid crystalline polymers with mesogenic groups modelling low molecular weight C smectics☆

The synthesis of comb-like polyacrylates and polymethacrylates with phenyl benzoate mesogenic groups is described. The LC phases formed by the polymers, the temperatures and heats of the phase transitions have been studied. The factors promoting the formation of such systems of inclined smectic mesophases are discussed.

Structural transformations in guttapercha on disturbance of the chemical regularity of the chains

A NECESSARY condi t ion for po lymer crystal l izat ion is t h a t the chain s t ruc ture should be regular. Any depar tu re f rom regular i ty hinders the crystal l izat ion processes and there m a y be considerable changes in the phys icomechanica l properties of the original polymer . The possibilities of crysta l l izat ion and s t ruc tu ra t ion in chemical ly i r regular polymeric sys tems were recen t ly deal t wi th in the su m m ary article by two of the present au thors [1]. Sys temat ic invest igat ion of the regularities in the s t ruc tura l var ia t ion of a po lymer when its regular chain s t ruc ture is g radual ly d i s turbed is of considerable scientific and pract ical interest since the l i tera ture contains ve ry lit t le in format ion in this field, and most of it is f r agmenta ry . The aim of the present work was to s t udy the effects of the degree of irregula r i ty of po lymer chains on the crystal l izat ion and s t ruc tu ra t ion in such systems, and also on the resu l tan t var ia t ion in cer ta in of the physicochemica! characteristics. The crystal l ized po lymer trans-l ,4-polyisoprene (gut tapercha) is a convenient object for this k ind of s tudy, since the regular i ty of its chains is easily dis turbed, for instance by adding halogen a toms to the chain. Below we give the results showing the var ia t ion in the physical s t ruc ture of gu t t ape rcha due to halogenation.

Polymers with biphenyl fragments in branches having a crystalline and liquid crystalline structure

Comparative studies have been made of the thermal properties and the structure of non-stereospecific, acrylic series polymers containing biphenyl groups in branches directly linked to the main chain, namely poly-p-biphenyl acrylate (polymer I), and also those with a separate flexible aliphatic branch, i.e. poly-p-biphenyl-(N-methacrylyl-ω-aminolaurate) (polymer II) and the poly-p,n-hexyloxy-p-biphenyl-(N-methacryl-ω-aminolaurate) (polymer III). All 3 polymers have been found to be capable of a crystallization due to the packing of the branches. Polymer I can exist in the “frozen” liquid crystalline state; polymer II forms an enantiotropic liquid crystalline phase. Infrared spectroscopy has been used on polymer III as example to examine the nature of the branch interactions in various states of phase of the polymer.