synopsisThe heats of fusion and the melting transitions of the crystallinity present in the side chains were determined for selected copolymers incorporating n-octadecyl acrylate or vinyl stearate. A major purpose of this investigation was to ascertain the effect of INTRODUCTIONMuch interest has centeredl8.2 on the crystallization phenomenon in copolymers in which one co-unit of the main chain is capable of crystallizing. The Flory theory of the equilibrium crystallization of polymers3 required that sequence length distribution, and not the chemical nature of the amorphous component, determbed the melting point depression. A very broad distribution of crystal sizes and lowered crystallinities were 3349 0

synopsisMechanical and solution properties, melting transitions, torsional stiffness temperatures, Tf, and selected modulus-temperature curves are presented for copolymers of the N-n-alkylacrylamides with vinylidene chloride. Copolymers were prepared at 6OoC across the range of compositions, using &s comonomers N-n-butyl-, octyl-, dodecyl-and oleyl-acrylamide, which have amorphous side-chains, and N-n-octadecyl acrylamide and n-octadecyl acrylate whose side-chains are crystalline. The mechanical properties reflected the effect of the decline in backbone crystallinity and the simultaneous development of strong intermolecular interactions in the amorphous stage. Copolymers were stiff or showed brittle failure across the compositional range except when intermolecular forces were reduced (with n-octadecyl acrylate) and side-chain crystallization eliminated (with N-oleylacrylamide). These systems and the n-dodecylacrylamide copolymers had yield strengths less than brittle strengths and substantial elongations.Backbone crystallinity w&s eliminated a t about 15 mole % amide and side-chain crystallinity vanished at less than 10 mole yo of the amide in the N-n-octadecylacrylamide series. No depression in side-chain melting point occurred with dilution by segments of vinylidene chloride. Over-all decline in the flex-temperature was the normal monotonic function of composition except that values increased in magnitude at high vinylidene chloride contents, the effect presumably being caused by the presence of crystallinity.An empirical equation was developed which permitted the calculation of Tf for any N-n-alkylacrylamide composition with any number of carbon atoms in the side-chain, above 3.

SynopsisCompositionally and structurally varied copolymers all containing n-octadecyl acrylate were prepared and evaluated as viscosity index improvers in a common base oil under conditions of low shear. Systems evaluated over a range of copolymer and blend composition were: copolymers of n-octadecyl acrylate with, respectively, methyl methacrylate, 2-ethylhexyl acrylate, and n-dodecyl acrylate; and homopolymers of poly(n-octadecyl acrylate), prepared with a wide range of molecular weights. Properties were compared with those of blends of commercial methacrylate copolymers (acryloids) which had been freed of their entraining liquid. Mixtures of base oil with copolymers of n-octadecyl acrylate and methyl methacrylate, compared at fixed SAE viscosities, were the most efficient of all blends studied. They had the smallest rate of change of viscosity with temperature (as measured by their ASTM slopes), particularly in the composition region of incipient polymer precipitation at room temperature. Efficiency of certain of these compositions was somewhat greater than that of the acryloids. A parameter that related concentration and weight-average molecular weight was used to correlate all of the data for ASTM slope and viscosity. Empirical relations developed by using this parameter enabled rheological data to be estimated that agreed within 6% of experimental values for the case of thermodynamically good base oil solvents. These data demonstrated the relatively small contributions of copolymer structure to viscosity index improvement.