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properties (transparency, refractive indices) and mechanical properties (elastic
modulus should not exceed one (1.5-1.7 MPa). To this material are
requirements. In - First, it should be biphasic composite that allows you to
combine hydrophilic properties and high oxygen permeability. In - the second
polymeric phase have to be contiguous. Only in this case the material is
permeable to both oxygen and water with dissolved substances. B - Third, the
material should have a sufficiently fine structure that is desirable that the
structural elements have been nanoscale dimensions or the order of the
wavelength of the incident light.
The first silicone - hydrogels that meet the above requirements, developed
by "CibaVision" and "Bausch & Lomb" [89]. They have high oxygen
permeability (Barrer 140 and 110) and simultaneously water - and at the level of
ion permeability known in ophthalmology hydrogel crosslinked polymer HEMA
[89]. But, to the organization of the production of silicone - hydrogel soft
contact lens specialists had to face with another problem. It was found that the
surface of the lens obtained copolymerization method in the form of siloxane
macromonomers, other silicon-containing monomers (TRIS or TMCK),
crosslinkers (e.g., ethylene glycol) and hydrophilic monomer (N, N -
dimethylacrylamide or VI) is hydrophobic, and that is enriched in siloxane
components. Due to higher concentration oksanovogo force component in the
material. The exact composition of silicone - hydrogels developed these
companies, unknown. But, judging by the size of the equilibrium water content
in the materials (24 and 36 wt.%), The content of polysiloxane phase should be
at least 70-80 wt. %. Probably due to thermodynamic reasons hydrophilic
moieties during synthesis of the polymer and the localized phase separation in
the bulk material. The problem was solved by the development of various
surface treatment methods silicone - hydrogel articles, including chemical and
physical methods [90-92].
Biphasic nature conetworks determines the characteristics of the
application of these materials for other. Purposes. The presence of hydrophilic,
hydrophobic phase can be considered as universal conetworks drug carriers and
others. Substances. For example, in [93] that meshes constructed from blocks of
poly-e-caprolactone HEMA polymer and capable of absorbing and then
releasing both lipophilic (dexamethasone - acetate) and the hydrophilic
substances (sodium phosphate). There are other areas of application and
associated with the manufacture pervaporatsionnyh membranes for the
separation of water-ethanol mixtures [94], gas separation membranes for oxygen
enrichment gas mixtures [26].
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