[Determination of surface energy of PS-PEO-PS triblock copolymers by inverse gas chromatography].

The surface energy(gamma sd) of the dispersive component of the triblock copolymers, poly(styrene)-poly (ethylene oxide)-poly(styrene)(PS-PEO-PS), was determined by using inverse gas chromatography(IGC). A series of linear alkanes were used to determine the free energy of adsorption (delta GCH2) of a CH2 group in a temperature range of 70 degrees C-120 degrees C, and gamma sd of PS-PEO-PS were calculated. The effects of the polymer composition and temperature on gamma sd values were discussed. IGC data indicated that gamma sd values of PS-PEO-PS were lower (gamma dPS-PEO-PS-1 = 16.99 mJ.m-2, gamma dPS-PEO-PS-2 = 17.98 mJ.m-2, 70 degrees C) than that of PEG (gamma dPEG = 21.74 mJ.m-2, 70 degrees C), and increased as the ethylene oxide content increased in PS-PEO-PS. The gamma sd was sensitive to temperature, decreased sharply with the increase of temperature. Linear relationships were obtained between the gamma sd and temperature (t, degree C), which were gamma dPE-PEO-PS-1 = 28.12-0.161t and gamma dPS-PEO-PS-2 = 28.23-0.148t.

[Study of the miscibility of polymer blends by inverse gas chromatography].

An investigation was made on the thermodynamic parameters chi'23 of the polymer system polyvinyl chloride (PVC)/ethylene-vinyl acetate copolymer(EVA) by inverse gas chromatogrphy(IGC), and the miscibility of the blends was studied by using chi'23 as judging foundation, and it was preliminary discussed the relation between chi'23 and composition of the blend, and molecules-chain structure of polymer, and temperature. The influence of the property of probes on chi'23 was also discussed. Results showed thermodynamic miscibility for PVC/EVA blend was accurately and directly indicated by chi'23. Experimental data confirmed the conclusion reported by other studies. It was immiscible for blends of which the acetate content was lower in EVA copolymer. The experimental temperature was favorable for improving miscibility of blends. The medium content in EVA copolymer resulted in partial miscibility for the blend, but the phase-seperation appeared when the experimental temperature was raised. This is in agreement with the previous studies on polymer blends. The apparent interaction parameter was found to be dependent on the chemical nature of the probe, the values of chi'23 were very different, but most experimental data show the same general trend with temperature and composition of blends.

[Study of the crystalline behaviors of polymer by inverse gas chromatography].

An investigation was made on crystallinity(Xc) and melting temperature(Tm) of the crystalline polymer polyethylene glycol(PEG) by inverse gas chromatography(IGC). The influence of the property of the probe and the coating weight of PEG in stationary phase on the data determined is discussed. And IGC data are compared with those got by differential scanning calorimetric (DSC) experiment. Results showed that IGC is a very useful technique for measuring the melting point and the degree of crystallinity of polymer samples since it does not depend on the assumptions about the properties of 100% crystalline polymer. IGC data indicated that the melting temperature of PEG was 67 degrees C and crystallinity was 89.7%. DSC data indicated the same results. The experimental data was found to be not related with the chemical nature of the probes, but depended on the coating weight of PEG on the supports.

[Separation model of small molecules with SEC columns and micellar mobile phase].

Small alkanol molecules were successfully separated with SEC method in combination with a micellar mobile phase. The separation model has been given in this system. The separation is based on the differential migration of the micelle and the surrounding water and the differential distribution of the solute between the micelle and aqueous phase, therefore, the separation mechanism is very similar to that of micella electrokinetic chromatography (MEKC). The retention volume of solute is related to the micellar concentration by theoretical treatment, through which the solute distribution coefficient between micelle and aqueous phase could be obtained. Two different SEC columns were employed for separation of some alkanols and the theoretical model is supported by the experimental results. The distribution coefficients obtained were in good agreement for these two columns.