Preparation of Nano-Particles of Poly(phenylsilsesquioxane)s by Emulsion Polycondensation of Phenylsilanetriol Formed in Aqueous Solution

Abstract

ABSTRACT:Spherical nano-particles of Poly(phenylsilsesquioxane) (PPSQ) were prepared by emulsion polymerization of phenylsilanetriol (PST) that had been formed in aqueous solution after hydrolysis of trichlorophenylsilane (TCP). The average size of the resultant particles was controlled from 30 nm to 110 nm in diameter by changing the amount of the emulsifier added to the solution. The PPSQ forming the particles was low molecular weight oligomer, consisting of silanol groups that can be utilized as functional groups for further chemical modification.KEY WORDS Poly(phenylsilsesquioxane) / Nano-Particle / Emulsion Polymerization / Trichlorophenylsilane / Poly(phenylsilsesquioxane) (PPSQ) is one of the most extensively investigated polymers of silsesquioxane and has been convinced to have wide application because of their supreme thermal and electrical properties. 1, 2 In 1960, Brown et al. first reported that the hydrolytic polycondensation of phenyltrichlorosilane (TCP) gave a PPSQ with ladder structure. 3 Its structure confirmation and formation mechanism, however, has ever since been controversial among the researchers in this field. In the general synthetic method for PPSQ, TCP is hydrolyzed in aqueous/organic bilayer system, and the resultant hydrolysate is extracted into the organic layer and subjected to the alkalicatalyzed dehydrative polycondensation in organic solvent such as toluene. Recently, we have shown that the hydrolysate extracted in the organic layer consists of oligomers of phenylsilanetriol (PST) that is the primary hydrolysis product. The monomeric PST is highly soluble in aqueous media and resides in the aqueous Scheme 1. Preparation of PPSQ by dehydrative polycondensation of PST formed from TCP. layer. We have also shown that PPSQ with a highly ordered ladder structure can be obtained when the monomeric PST isolated from the aqueous layer is subjected to the KOH-catalyzed polycondensation in refluxing toluene. 4, 5 Furthermore, we synthesized a tetracyclo(phenylsilsesquioxane) (T 4 ) by the oligomerization of PST by the catalysis of a weak base, NaHCO 3 , and then polymerized it by the KOH-catalyzed polycondensation in toluene to obtain the ladder PPSQ. 6 More recently, we conducted the polycondensation of PST in a refluxing toluene/water bilayer system added with a phase transfer catalyst to obtain PPSQ in high yield (Scheme 1) without passing the isolation step of PST and its oligomers. 7 With increasing interest in designing micro-and nano-structured materials, many attempts have been made to obtain nano-particles with suitable shapes. 8,9 Minami et al., for example, prepared PPSQ particles from organoalkoxysilane by using the sol-gel technique 709

Graft Polymerization of Dimethylacrylamide onto Polysilsesquioxane Containing Mercapto Groups

“…7 Generally, the chemical shifts of T 2 and T 3 were reported to vary with the difference of structures and molecular weights. 27,28 In the 29 Si NMR spectra of oligo-and poly(phenylsilsesquioxane), T 3 silicone signal of oligocyclic one is observed at À64:1 ppm and that of polymerized one is at À83:7 ppm. 28 The later chemical shifts of the polysilsesquioxane, M n of which is 53800, is explained by the environmental homogeneity of each repeating unit.…”

Formation of Stable Nanoparticles of Poly(phenyl/methylsilsesquioxane) in Aqueous Solution

“…SDS was first examined as an anionic emulsifier that had been found out to be quite effective for obtaining the PPSQ nanoparticles. 9 In fact, when the emulsion polymerization was conducted at 90 • C for 16 h with 0.5-3.0 wt% of SDS relative to the amount of the aqueous medium, a transparent colloidal dispersion was formed without coagulation occurring. When the aqueous layer was directly heated at the same conditions without the emulsifier added, rapid coagulation was induced.…”

“…8 We also disclosed the preparation of nanoparticles of PPSQ having an average diameter of 30-110 nm by conducting the emulsion polymerization of the TCP hydrolysate after the addition of an emulsifier. 9 This was the first success in preparing the nanoparticles of PSQ.…”

Macroporous materials by self-assembly of linear oligo(phenylsilsesquioxanes).

“…However, the literature reports concern poly(phenylsilsesquioxane) microparticles obtained in a modified Stöber route [18,19] emulsion polymerization [20], a template-free two-step acid-base catalyzed sol-gel process [21,22] and base catalyzed oil-in-water emulsion polycondensation [19]. Phenylsilsesquioxane particles of 'core-shell' structure show both thermoplastic and thermosetting properties [23,24].…”