ISSN:
0022-3832
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Physics
Notes:
Poly-n-octyl methacrylate, prepared by the emulsion technique, was fractionated three times by the fractional precipitation procedure to obtain eight fractions. Relationships between viscosity and weight-average molecular weight were obtained in both an ideal solvent, n-butanol, and a nonideal solvent, methyl ethyl ketone. These relationships are represented by the equations, [η]16.8Θ = 2.68 × 10-4M0.50w [η]23 = 4.47 × 10-5M0.69w, respectively. The effect of the size of the pendant groups (-methyl, -ethyl, n-butyl, -n-hexyl, and -n-octyl ester) on the degree of extension of macromolecules in ideal solvents is discussed. It was found that, initially, as we progress from polymethyl to poly-n-butyl methacrylate, the degree of flexibility of the macromolecule increases as the size of the pendant group increases. These results are believed to be due to the short-range interference effect of the solvent molecule on the degree of free rotation of the macromolecule. However, it was found that poly-n-hexyl methacrylate chains have considerably greater chain extension than any of the other three polymers. This expansion of poly-n-hexyl methacrylate chains is a result of the steric effect of large pendant units. From the results obtained for n-octyl polymer, it is evident that, in spite of further increase in the size of the pendant group by —(CH2)2—, there is a substantial contraction in the n-octyl polymer chain. The reason for this reversal in the polymer chain expansion is not clearly understood at present.
Additional Material:
8 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/pol.1958.1203312645
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