Abstract
Polysilanes with sterically bulky substituents, -[2-( $R^1R^2$-phenyl)propyl]Si[$R^3$]-, such as poly(2-phenylpropyl)(n-hexyl)silane [$R^1=R^2$=H, $R^3$=n-hexyl] were prepared by Wurtz-type coupling reactions with Na using a sonochemical method. The high-intensity ultrasound provided the formation of high quality Na dispersion in toluene and its active surface which was important for the synthesis of polysilanes in Wurtz-type coupling reaction was freshly and continuously regenerated during the process. The polysilanes products were mixtures of high molecular weight polymers with $\={M}_W$ of ∼$10^6$ and low molecular weight polymers with $\={M}_W$ of ∼$10^3$. It was found that the formation of high molecular weight polymerr was greatly influenced by the substituents $R^3$, directly attached to Si. On the contrary, changes on substituents ($R^1, R^2$) gave no influences at all. Overall yields for polysilanes were 75-99% in general but high molecular weight polysilanes were obtained as a major product when substituent $R^3$ is n-hexyl group and low molecular weight polysilanes were obtained as a major product when substituent $R^3$ is cyclohexyl and 2-phenylethyl groups. Effects of reaction conditions to polysilane yields were investigated.
크기가 큰 치환기의 폴리실란-[2-($R^1R^2$-phenyl)propyl]Si[$R^3$]-[예:$R^1=R^2$=H, $R^3$=n-hexyl; 폴리(2-페닐프로필)(n-헥실)실란]을 초음파 화학적 방법을 사용하여 Wurtz 축합반응에 의해 합성하였다. 초음파는 톨루엔 용매 중 금속 나트륨을 분산시켜 작은 크기와 높은 표면 활성의 나트륨을 형성하였으며 이에 의해 Wurtz 축합반응이 진행되었고 또한 초음파는 부 생성물인 염화나트륨이 나트륨 표면에 침착되는 것을 방지하여 표면활성이 지속적으로 유지되도록 하여 효율적인 반응이 기대되었다. 폴리실란 생성물은 저분자량의 중합체(분자량~$10^3$)와 고분자량의 중합체(분자량~$10^6$)의 혼합물로 얻어 졌다. 전체 수득률은 75-99% 이었으나 $R^3$가 n-hexyl기인 경우에는 혼합비율은 고분자량 중합체가 주 생성물로, cyclohexyl 또는 2-phenylethyl기인 경우에는 저분자량 중합체가 주 생성물로 얻어져 폴리실란의 치환기 종류에 영향을 받는 것으로 나타났으나 $R^1, R^2$의 변화는 영향을 나타내지 않았다.