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angle of 65 ° [108]. This value is somewhat higher than that of the amphiphilic
PRT described in [100]. Perhaps this is due to differences between the UPU and
the floor - the UPU, in which the linear macromolecules of PVP have greater
mobility as compared with a crosslinked hydrophilic polymer in the UPU.
The only disadvantage of silicone-hydrogel PRT [100] - their relatively
rough structure, as evidenced by the opacity of the material in a dry state. Upon
hydration the hydrophilic and silicone refractive indices phase aligned, and the
material becomes transparent, which allows its use for the manufacture of soft
contact lenses. Opacity silicone-hydrogel in a dehydrated state, in principle, is
not critical index, although some restrictions on its use. When using silicone-
hydrogel soft contact lenses at low humidity or when there is insufficient
emphasis on the eyes tear fluid (in the pathology of "dry eye syndrome"),
clouding of the material can occur.
There are several approaches to solving this problem. One of them is
associated with an increase in the formation rate of the second grid was
considered earlier in Example PDMS IPN-polymethacrylic acid [99]. The
second approach can be implemented by varying the parameters of the first grid.
IPN morphology (domains second mesh size) depends on the degree of
crosslinking mesh obtained in the first step in the synthesis of silicone mesh. The
smaller size of the cells of the first grid, that is less than the distance between
crosslinks, the smaller the mesh size of the hydrophilic domains formed in the
second process stage. These data are given in [48] and [102]. In the latter in
obtaining silicone - based hydrogel polysiloxane copolymer VP-N, N-di-
methyl acrylamide crosslinked polysiloxane synthesized by reacting
gidridsoderzhaschego oligosiloxane with M = 1 x 103 and a vinyl-containing
oligosiloxane with M = 1. 7 x 104. Manufactured material is opaque in the dry
state, indicating that the large dimensions of the structural elements that scatter
light. And the synthesis of vinyl-containing polysiloxane used oligosiloxane grid
with M = 7 x 103, allowing to form a denser grid, that the resulting silicone -
transparent hydrogel is hydrated, in dry conditions [48].
The thermodynamic incompatibility of the hydrophilic polymer and
polysiloxane greatly complicates the formation of the composite material with a
fine structure and a highly interfacial boundary. The use of large amounts of
solvent improves the situation somewhat, but does not give a final decision,
since the formation of highly swollen gel fragile hinders him subsequent
technological operations. In [48] and [109] proposed a new method of forming a
silicon-hydrogel IPN comprising obtaining a hydrophilic phase, a precursor to
the second stage of the synthesis of sequential IPN. The synthesis includes the
steps of preparing a crosslinked polysiloxane by hydrosilylation reaction as
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