Circular dichroism of optically active poly(dialkylsilane) aggregates in microcapsules.
Poly[n-hexyl-(S)-3-methylpentylsilane] aggregates confined in microcapsules to keep the aggregation number and ranging in average polymer mass m(p) in a microcapsule from 2 x 10(-)(16) to 2 x 10(-)(14) g were studied by circular dichroism measurements in ethanol (a nonsolvent) and tetrahydrofuran (an associative solvent at low temperature) at various temperatures. The weight-average molecular weight M(w) and the polydispersity index (the ratio of M(w) to the number-average molecular weight) of the polysilane sample were 6.6 x 10(4) and 1.07, respectively, and the average number of polymer molecules in each capsule was estimated to be 1.9 x 10(3) for m(p) = 2 x 10(-)(16) g and 1.7 x 10(5) for m(p) = 2 x 10(-)(14) g. The size of each aggregate did not affect the optical activity because the circular dichroism thus obtained was proportional to m(p) under the same conditions in the investigated m(p) range; on the other hand, the peak height of the circular dichroism in tetrahydrofuran had a significant hysteresis between 0 and 25 degrees C. Moreover, the circular dichroism appreciably reflected the prepared method, that is, the temperature and solvent; in other words, the aggregates memorized the initial conditions in their stacking structures.
Terao
Ken
K
Department of Biological and Chemical Engineering, Faculty of Engineering, Gunma University, 1-5-1 Tenjin-cho, Kiryu 376-8515, Japan. kterao@chem.sci.osaka-u.ac.jp
Kikuchi
Noriaki
N
Sato
Takahiro
T
Teramoto
Akio
A
Fujiki
Michiya
M
Dobashi
Toshiaki
T
D000478:Alkylation; D002214:Capsules / Q000737:chemistry; D002942:Circular Dichroism; D000431:Ethanol / Q000737:chemistry; D005663:Furans / Q000737:chemistry; D010316:Particle Size; D011108:Polymers / Q000378:metabolism*; D012821:Silanes / Q000737:chemistry*; D013696:Temperature
D002214:Capsules; D005663:Furans; D011108:Polymers; D012821:Silanes; D000431:Ethanol; C018674:tetrahydrofuran