Molecular weight and molecular weight distributions in synthetic polymers

Molecular Weight Profiles of Proanthocy Anidin Polymers

The MW profiles of proanthocyanidin polymers (condensed tannins) from 32 samples representing a wide range of plant tissues of many different species have been obtained by gel permeation chromatography of the peracetate derivatives. The tannins vary widely in MW, with Al. values for the peracetates in the range 1600-5500. The MW profiles vary greatly from those with narrow, rather smooth distri...

Dynamic Crossover in Polymers, Role of Molecular Weight

One of the most characteristic features of glass-forming liquids is the sharp slowing down of relaxation times, τ, upon cooling. In these materials relaxation dynamics exhibit a non-Arrhenius temperature dependence usually described by Vogel-Fulcher-Tamman (VFT) relation [1]. However, for majority of glassforming liquids it is impossible to fit data in the entire temperature range with a single...

Low molecular weight components of polymers used in packaging.

The increasing use of polymers in packaging of foods and drugs focuses attention on the possible chronic toxicity relations of migrants from these polymers to the contents. Such migrants can arise from residues and additives in the polymers from manufacturing processes used in fabrication of packages. The origin and chemical nature of potential migrants, the methods of transfer, and principles ...

Rheological Method for Determining Molecular Weight and Molecular Weight Distribution

The gamma distribution model for pulsed-field gradient NMR studies of molecular-weight distributions of polymers.

Self-diffusion in polymer solutions studied with pulsed-field gradient nuclear magnetic resonance (PFG NMR) is typically based either on a single self-diffusion coefficient, or a log-normal distribution of self-diffusion coefficients, or in some cases mixtures of these. Experimental data on polyethylene glycol (PEG) solutions and simulations were used to compare a model based on a gamma distrib...