SANS Studies at Higher Angles

Measurements have been made up to the q region 0.02—0.2 A the curves of q Ivs.q i20K now been obtained for PS, PE, PP, and PEO. This information has been used to evaluate models of the structure of semi-crystalline polymers by Yoon and Flory and they were able to show that in the case ofPE the calculations based on an irregular re entry model fitted the experimental data. Similar calculations by Fischer on PEO also supports irregular re-entry. Sadler and Keeler have studied solution-grown PE crystals and obtained information of the trajectory within the crystals. They concluded that adjacent fold re-entry occurs with the latter but not with melt-crystallized polymer. 

It is now possible unambiguously to measure the partition of comonomer units between crystaUine and amorphous phases in polymers. By combining SANS and SAXS studies in the q range 0.01 to 0.2 A, measurements can be made of the difference Ap between the mass densities of the crystalline and disordered regions as well as the concentration fluctuations of the comonomer units. One example studied was that of randomly chlorinated linear polyethylene in which the partition (y) of CHQ units between phases was measured at different concrai-trations of CHCl units, Xf- At xp = 1-0 mole per cent, y = 1, showing that most of the non-crystallizable co-imits are excluded from the crystalline regions. 

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