Polysiloxane nanocomposites systems

Historically, polysiloxane elastomers have been reinforced with micron scale particles such as amorphous inorganic silica to form polysiloxane microcomposites. However, with the continued growth of new fields such as soft nanolithography, flexible polymer electronics and biomedical implant technology, there is an ever increasing demand for polysiloxane materials with better defined, improved and novel physical, chemical and mechanical properties. In line with these trends, researchers have turned towards the development of polysiloxane nanocomposites systems which incorporate a heterogeneous second phase on the nanometer scale. Over the last decade, there has been much interest in polymeric nanocomposite materials and the reader is directed towards the reviews by Alexandre and Dubois (4) or Joshi and Bhupendra (5) on the subject. 

These few examples show how the use of nanocomposite systems with hetero polysiloxane type of matrices leads to interesting properties for applications. Further developments using these basic systems are transparent controlled release coatings for anti-fogging systems [41], anti-corrosive systems for metal protection [42], and nanocomposite optical bulk materials [43],... 

It is reasonable to link the mass loss with the observed changes in thermal stability and dielectric response, indeed some of this material that is evolved from the systems on aging is likely to be water and the reaction residues implicated as pro-degradants. However, the level of material lost the ongoing nature of the process and the clear link once again with a moist air environment points to an explanation other than simple passive loss of volatile residues from the nanocomposites. Cleary, an identification of this volatile material is desirable if the nature of the aging processes occurring within these polysiloxane nanocomposites is to be elucidated. 

For the synthesis of the nanocomposites, additionally to the reaction principles described above, nanoscaie particles have to be generated within or added to the hetero polysiloxane composite matrix. As described elsewhere [26], the sol-gel process, is a suitable means. It can be considered as a growth process from solution where a controlled growth reaction takes place, that leads to a stabilized colloidal system and thus avoiding precipitation. 

Summarizing, the in-situ growth of nanoscale particles in hetero polysiloxane type of matrix systems leads to an interesting type of nanocomposites, which is of special interest for application due to its... 

L. Su, Preparation of polysiloxane/perfluorosutfonic acid nanocomposite membranes in supercritical carbon dioxide system for direct methanol fuel cell, Int. J. Hydrogen Energy, 34 (2009) 6892-6901. 

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