摘要:

AbstractA study has been made of the marked effect of solvent on the stereoregularity of poly (methacrylic acid) prepared by the radical polymerization of methacrylic acid initiated by Co60gamma radiation. The specific interaction of the solvent with the monomer and the growing polymer chains, leading to particular structures at the growing chain end, leads to the observed effect on the stereoregularity of the polymer. It is apparent that solvents of intermediate hydrogen bonding strength and bulkiness lead to highly syndiotactic polymer. Thus poly (methacrylic acid) prepared at −78°CC in a 20% by volume solution of methacrylic acid in 2‐propanol contains 95% syndiotactic triads. The effect of the steric hindrance of the solvent is amply demonstrated by the fact that polymerization in 2‐methylcyclohexanol results in the highest degree of syndiotacticity at 0°CC (82% syndiotactic triads) but yields polymer having only 69% syndiotactic triads at −78°CC. This is in contrast to the usual effect on stereoregularity upon lowering the temperature of radical polymerization. The detailed mechanism of this polymerization and its relation to the polymerization of other monomers capable of hydrogen bonding to solvents will be discussed with specific reference to the particular structures that may give rise to the observ

ISSN:0360-8905    

DOI:10.1002/polc.5070440123

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1974

数据来源: WILEY

摘要:

AbstractThe depolarization ratio ρ of the 1002 cm−1band in polystyrene has been measured as a function of temperature (20

ISSN:0360-8905    

DOI:10.1002/polc.5070440124

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1974

数据来源: WILEY

摘要:

AbstractElectro‐optical properties of solutions of several cellulose esters in dioxane have been investigated. It was shown that macromolecules of these esters are characterized by high equilibrium and kinetic chain rigidity. The coincidence in signs of the Kerr and Maxwell effects in solutions of the samples reveals general relationships exhibited by all rigid‐chain polymers for which the longitudinal geometric axis of the molecule (direction of the greater geometric length) is also the symmetry axis of its polar and optical properties.Experimentally found dependences of hydrodynamic and electro‐optical properties of solutions of cellulose carbanilate (CC) on molecular weight (Mw) show that with the increase inMwthe conformation of the CC molecules varies from a faintly curved rod to a rigid Gaussian coil. A study on the dependence of the equilibrium constant of the Kerr effect onMwleads to the same conclusion. Besides, in Gaussian region (highMw) the Kerr effect depends on the longitudinal (with respect to the chain) component of the dipole moment formed by the C‐O bonds making a part of the glucoside ring. At lowMthe transverse components of the monomer dipoles begin to play an important part in birefr

ISSN:0360-8905    

DOI:10.1002/polc.5070440125

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1974

数据来源: WILEY

ISSN:0360-8905    

DOI:10.1002/polc.5070440102

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1974

数据来源: WILEY