This paper reports the spontaneous formation of a high-molecular weight multiblock PSi copolymer made up of i-butyl-n-decyldichlorosilane (M1) and methyl-3,3,3-trifluoropropyldichlorosilane (M2). The copolymer was formed under conditions of simultaneous addition via a Wurtz-type condensation reaction with sodium in refluxing toluene, without the help of a cocatalyst. The multiblock structure of poly [(i-butyl-n-decylsilane) x -b-(methyl-3,3,3-trifluoropropylsilane) 1-x ] (PSi1) was characterized by means of 29 Si{ 1 H} NMR, UV absorption, photoluminescence (PL), and photoluminescence excitation (PLE) measurements. The average block lengths (L) of the i-butyl-n-decylsilane (Si3) block and the methyl-3,3,3-trifluoropropylsilane (Si4) block in PSi1 were successfully evaluated by a block-selective scission technique using tetra-n-butylammonium fluoride (TBAF). This technique allowed for the selective decomposition of Si4 in PSi1 under reaction conditions when the concentration of TBAF and reaction time were optimal. The L values of Si3 and Si4 were, respectively, ∼4.8 nm (corresponding to an averaged repeating unit of n ∼ 26) and ∼3.5 nm (n ∼ 19). The copolymerization mechanism of PSi1 was further studied using the time-conversion curves of M1 and M2 by gas chromatography. Gel permeation chromatography using a photodiode array UV detector and 1 H NMR measurements were used to analyze the PSi1 product. Upon simultaneous addition of M1 and M2 comonomers, only M2 initially formed the Si4 oligomer (M n ∼ 3 000), and after a certain period of polymerization time, M1 abruptly copolymerized with the Si4 oligomer, followed by formation of the multiblock PSi1 copolymer.

This paper reports that fluorinated PSis with 3,3,3-trifluoropropyl and linear alkyl side chains (F-PSi)s demonstrated monovalent anion size dependent fluorescence quenching, which has potential as a novel type of chemosensor, "monovalent anion indicator". The extent of the fluorescent quenching was linearly increased by a decrease in the surface charge density of the monovalent anions. In addition, sensitivity toward monovalent anions was modulated by choosing an adequate length of linear alkyl chains, which efficiently served as a soft but strict molecular sieve for the monovalent anions. In contrast, nonfluorinated PSi did not show such an ability to discriminate monovalent anions, suggesting that the positively charged Si main chain stimulated the electrostatic interaction with monovalent anions.

A semiflexible polysilane copolymer bearing 3,3,3-trifluoropropyl and n-decyl side chains formed an organogel in nonpolar organic solvents. Weak Si/FC interchain/intrachain interactions were formed between the Si main chain and fluoropropyl side chain, and acted as noncovalent crosslinks. Long alkyl (n-decyl) groups acted as solvophilic moieties that effectively absorbed and retained organic solvent molecules. Furthermore, the relatively rigid main chain was also important for the gelation ability of the material. The existence of Si/FC interchain interactions was first demonstrated by careful IR measurement and analysis using a model silane molecule. Hierarchical structures at the meso-and nano-scale levels were successfully characterized by AFM, cryo-HR-TEM, IR, and 19 F{ 29 Si}-NOE NMR experiments.

Selective scission of the positively charged main chain of polydialkylsilane using tetrabutylammonium fluoride was utilized for facile chemical degelation of polymer-based organogel. The degelation mechanism was characterized by combinational analyses with photodiode array-equipped size exclusion chromatography, GC/MS, and FTIR measurements.

A soluble Si-Si bonded polymer (polysilyne, SNP) bearing n-butyl groups (BSNP) has been reported to exhibit a green photoluminescence (PL) at 540 nm (2.30 eV). However, BSNP gradually changed to a colorless solid because of auto-oxidation within a few weeks when the polymer was stored in the absence of light without special care. Herein, we demonstrate the photophysical properties of SNP carrying 3,3,3-trifluoropropyl (TFP) side groups (FSNP), which remains unaffected by autooxidation. This stability against oxidation may be possibly attributable to intra-and inter-molecular CF-Si interactions between the electron-donating Si-Si main chain and the electron withdrawing TFP side groups. FSNP in polar tetrahydrofuran (THF) exhibited an almost pure-blue PL peak at 450 nm (2.76 eV), whereas in non-polar n-octane, it emitted a near-UV peak at 337 nm (3.68 eV), possibly, because of the CF-Si interactions. Additionally, thin films of FSNP exposed to air and in THF exhibited excellent resistance to air oxidation for at least one month, as determined by the lack of any changes in its PL, IR, and Raman spectra. From Gaussian03 calculations (TD-DFT, 6-31G* basis set, B3LYP) of trans-perhydrosiladecaline partially substituted with TFP and n-butyl groups as models of FSNP and BSNP, the most essential roles of TFP groups suggested that (i) the lowest Sis-Sis* transition state becomes the allowed transition by introducing strong polarity to the SNP skeleton and (ii) both the HOMO and LUMO energy levels are significantly stabilized, which provides the observed stability toward air oxidation. The air stability was effective in copolymers carrying TFP and n-butyl groups (FBSNP). However, FSNP and FBSNP that had been pyrolysed at temperatures greater than 500 C exhibited no such air stability because of the loss of the TFP groups.