Стр. 125 - ДЛЯ ППС

Упрощенная HTML-версия

Mesh silicon formation reaction and radical copolymerization of the
hydrophilic monomer (HEMA, VP, N, N-dimethyl-acrylamide, etc...) with a
crosslinking monomer material under the action of initiators or photoinitiation.
The process was carried out in a solvent (chloroform). After completing the
reaction and removing the solvent, transparent, flexible films were obtained. The
transparency of the material indicated the formation of a thin composite
structure. But the possibility of its use for the manufacture of silicone-hydrogel
soft contact lenses extended wear limited low-hydrophilic component, but it can
not provide the minimum acceptable content of water in the hydrogel. It is
known [96] that in silicone-hydrogels percolation threshold, where the hydrogel
is realized continuous phase and water - and ion permeability of the material is
achieved only when the water content of the hydrogel composite of at least 20
wt. %.
[97] describe the preparation of polybutadiene simultaneous IPN-PEO
hydrophilic component containing 20-80 wt. %. The hydrophilic mesh in the
system formed by radical copolymerization of mono- and PEO dimethacrylate
derivatives and polybutadiene phase oligodienes formed by reacting with
terminal hydroxyl groups and isocyanate crosslinker Desmodur N3300 (
"Bayer") catalyst in the presence of di - butildilaurinata tin. The authors [97]
have shown true simultaneous IPN formed at high levels in the reaction system
of methacrylic derivatives PEO. Both grid formed about the same rate, at the
same time received the UPU structure was very heterogeneous, which is
indicated by the opacity of the material.
When the content of the reaction system is less than 60 wt.% PEO
formation rate polybutadiene grid is much higher, that is, there was a formation
consistent UPU and managed to produce a transparent material.
Similar results are presented in [98] in the formation of semi-PDMS IPN
PIP. Optical properties and electron micrographs of the materials showed that a
homogeneous structure is formed only in successive semi-IPN. If the process is
carried out on the floor of simultaneous synthesis technology - the UPU, the
material is opaque. To better control the morphology of the composite material
is expedient to synthesize successive UPU. In this embodiment, the receiving
material influence the kinetics of the formation of the hydrophilic and
hydrophobic mesh is less important, although completely exclude the role of the
speed of formation of the second grid of the UPU can not. If the rate of
formation of the polymer network in the second stage higher than the rate of
relaxation processes, the rapid emergence of intermolecular entanglement can
eliminate the phase makrorazdelenie. In other words, in these conditions, the
freezing thermodynamically unfavorable morphology with a small domain size
122