Gel permeation chromatograph interface to collect solvent‐free polymer fractions for composition drift analysis

Abstract

An interface is described that is capable of stripping solvent from polymer solutions emerging from an interfaced high‐temperature gel permeation chromatograph. The chemical composition of each solvent‐free polymer fraction is then determined using Fourier transform infrared (FTIR) or other techniques to obtain the composition drift (CD) pattern of the polymer (i.e., variation of chemical composition as a function of molecular weight). The interface consists of a vacuum oven into which an ultrasonic nebulizer and a stepper motor have been incorporated. The stepper motor drives a fraction collector, equipped with a set of KBr plates, onto which the nebulized polymer solution is sprayed. The temperature and pressure of the interface are maintained so as to strip the solvent from the chromatographic effluent as it impinges on the collector substrates. The technique, which had been applied to the % ethylene CD of ethylene‐propylene rubbers, is employed in the analysis of a block copolymer reaction product. In the example given, the CD pattern of the reaction product generated is simulated along with the observed molecular weight distribution pattern to arrive at the approximate composition of the reaction product. For many applications, this approach eliminates the need to carry out tedious solvent/nonsolvent fractionations commonly employed in the characterization of the compositional heterogeneities in block copolymer reaction products.

T∥ from the temperature dependence of carbon‐13 NMR correlation times τc

“…' This reduction likely results from there being six data points instead of seven as in all other photoenlargements of published plots in Ref. 10.…”

“…Visual inspection of Figure 2 in Ref. 10 and of our extrapolated generic line in Figure 1 suggested that T/Tg reaches an asymptotic limit (T/T,), at about 1.21 and a log 5, of -6 or longer. I t also appeared likely from their Figure 2 that individual polymers would exhibit (T/Tg), values at an associated log rc that was polymer specific, depending on flexibility of the chain.…”

“…dSimiIar to inset to 10, and the number of data points are few, we have not employed the more rigorous statistical methods that we normally use?1 R2 is considered adequate for the data available. The inset to Figure 4 shows a residuals plot that is not too significant.…”

Other Modes of Detection

“…Several types have been used including ultrasonics [95,121]; monodisperse aerosol generators (MAGIC) [92,[96][97][98][99][100][101]; and ones for gradients, which can be programmed to change temperature as the mobile phase changes [74,102]. Several types have been used including ultrasonics [95,121]; monodisperse aerosol generators (MAGIC) [92,[96][97][98][99][100][101]; and ones for gradients, which can be programmed to change temperature as the mobile phase changes [74,102].…”

Monitoring the grafting of epoxidized natural rubber by size‐exclusion chromatography coupled to FTIR spectroscopy

“…Aluminium foil was placed on the underside of the disk, allowing double absorption through reflection of the IR beam. Further improvements were made to the nebulization of the aerosol 10,11 and later a commercial company started manufacturing and selling analytical instruments that operate on this concept. 12 In the years following the major contributions to epoxidized natural rubber (ENR) research, not much emphasis was placed on the analysis of these samples.…”