Abstract
The preparation of TEG- [tri(ethylene glycol) monomethyl ether] and PEG- [poly(ethylene glycol) monomethyl ether] terminated carbosiloxane and carbosilane dendrimers of the 1st -3rd generation is discussed. Alcoholysis of Si(OCH2 CH2 CH2 SiMeXCl)4 (1a , X = Me; 1b , X = Cl) with HO(CH2 CH2 O)n Me (2a , n = 3, TEG; 2b , n = 7.3, PEG) gives the appropriate dendrimers Si[OCH2 CH2 CH2 SiMe2 O(CH2 CH2 O)n Me]4 (3a , n = 3; 3b , n = 7.3) and Si{OCH2 CH2 CH2 SiMe[O(CH2 CH2 O)n Me]2 }4 (4a , n = 3; 4b , n = 7.3). In an analogous manner the 2nd and 3rd generation carbosiloxane dendrimers Si(OCH2 CH2 CH2 SiMe{OCH2 CH2 CH2 SiMe[O(CH2 CH2 O)n Me]2 }2 )4 (6a , n = 3; 6b , n = 7.3) and Si[OCH2 CH2 CH2 SiMe(O(CH2 )6 SiMe{OCH2 CH2 CH2 SiMe[O(CH2 CH2 O)3 Me]2 }2 )2 ]4 (8 ) are accessible. The preparation method for 3 , 4 and 6 can successfully be transferred to Si(CH2 CH2 CH2 SiMeCl2 )4 (9 ) and Si[CH2 CH2 CH2 SiMe(CH2 CH2 CH2 SiMeCl2 )2 ]4 (11 ). The carbosilane dendrimers Si{CH2 CH2 CH2 SiMe[O(CH2 CH2 O)n Me]2 }4 (10a , n = 3; 10b , n = 7.3) and Si(CH2 CH2 CH2 SiMe{CH2 CH2 CH2 SiMe[O(CH2 CH2 O)3 Me]2 }2 )4 (12 ) are obtained in very good yield. However, the Si-O bonds in 3 , 4 , 6 , 8 , 10 and 12 may be cleaved in the presence of a protonic source. Therefore, the carbosilane dendrimers Me2 Si[CH2 CH2 CH2 SiMe2 CH2 CH2 CH2 O(CH2 CH2 O)3 Me]2 (15 ), Si[CH2 CH2 CH2 SiMe2 CH2 CH2 CH2 O(CH2 CH2 O)3 Me]4 (17 ) and Si{CH2 CH2 CH2 SiMe[CH2 CH2 -CH2 SiMe2 CH2 CH2 CH2 O(CH2 CH2 O)3 Me]2 }4 (19 ) were synthesized by the hydrosilylation of CH2 =CHCH2 O(CH2 CH2 O)3 Me (14 ) with Me2 Si(CH2 CH2 CH2 SiMe2 H)2 (13 ), Si(CH2 CH2 CH2 SiMe2 H)4 (16 ) or Si[CH2 CH2 CH2 SiMe(CH2 CH2 CH2 SiMe2 H)2 ]4 (18 ) in the presence of the Karstedt catalyst. ESI-TOF MS studies reveal that 3a , 10a , 12 , 15 , 17 and 19 form complexes with Na+ and K+ cations, which enables such species as possible ionophores for chemical sensors.
Key words
carbosilane dendrimers - carbosiloxane dendrimers - chemical sensors - poly(ethylene glycol) monomethyl ether - tri(ethylene glycol) monomethyl ether
