Search

A homologous series of poly(n-alkylmethylsiloxanes), [SiMe(R)O]n, were prepared by cationic ring-opening polymerization (ROP) of cyclotrisiloxanes containing n-alkyl substituents, such as C2H5, n-C3H7, n-C4H9, n-C5H11, and n-C6H13, on the Si. The resultant polymers were characterized by NMR, GPC, and DSC measurements. All of these asymmetrically substituted polymers were obtained in high molecular weight form and were found to have an atactic configuration. Their glass transitions were found to increase smoothly from Et to n-Hex (i.e., −139, −120, −115, −111.9, and −108 °C, for Et to n-Hex, respectively). These Tgs are much lower than those of the corresponding polyolefins, [C(H)(R)CH2]n. Moreover, in the case of these polyolefins, the Tgs decrease continuously from R = Me to n-Hex. The calculated Tgs for the polysiloxanes that were obtained by using published empirical equations show the same general trend as the experimental values.

A general method for introducing various side chains onto a highly branched polysilaethylene (HBPSE) backbone is described. This method starts with a commercial oligomer mixture which has a highly ...

Polysilaethylene ([SiH2CH2]n) (PSE) and deuterated polysilaethylene ([SiD2CH2]n) have been examined by both vibrational spectroscopy and X-ray diffraction methods above and below the crystallization/melting transition at −20 °C. The results confirm previous indications that PSE crystallizes in an all-trans conformation analogous to that found for its all-carbon analog, polyethylene. Raman spectroscopy reveals the appearance of a sharp band at 706 cm-1 attributable to the symmetric Si−C stretching vibration when PSE is cooled below 0 °C, while wide-angle X-ray diffraction shows the existence of a crystalline form with a monoclinic unit cell (a = 5.70 A, b = 8.75 A, c = 3.25 A; γ = 97.5°) whose dimensions compare closely to the calculated repeat distance using the planar zigzag conformation of PSE. The calculation of the IR spectra by ab initio methods (Hartree−Fock level of theory) using the 3-21G* and 6-31G* basis sets agrees well with the experimental IR results. Through the use of the calculated IR spec...

The molecular structure of the monosilicon analog of poly(ethylene), poly(silylenemethylene), CH3[SiH2CH2]nSiH3, or poly(silaethylene) (PSE), was characterized by means of high-resolution 1H, 13C, ...