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of the drug from the - to the sharp decrease of the diffusion coefficient of
substance. By increasing the pH to 7.4 ionized polymer and hydrogel swells
rapidly. As a result, the secondary release of the drug starts from a hydrogel. The
IPN hydrogel occur the same processes, but in the presence of the drug carrier
nonionic grid prevents the rapid collapse or swelling of the hydrogel
composition that smooths the "explosive" nature of drug release. The release rate
of the substance is reduced even more if it contains the cationic nature of the
functional groups, interact with the anionic groups of the hydrogel [41].
The combination of AMS mesh PMAA and PIP hydrogel makes the pH -
and temperature-sensitive [44]. Although the latter property is realized only PRT
enriched PIP, and at low pH at which ionization links acid is suppressed, and the
PRT swellability in water is reduced from - the formation of a relatively
hydrophobic interpolymer complexes by hydrogen bonding between the
carboxyl and amide groups .
Group ionic-nonionic UPU - new ion exchange materials, including mesh
nonionic copolymers of acrylonitrile (AN) - PE and the ionic copolymers of the
AN-VP-2-acrylic-Medo-2-methyl-1-propane sulfonic acid (AMSK) [47, 48].
In the hydrated state, these copolymers may be used as a polymer electrolyte
membrane for fuel cells. First ion exchange membranes based on copolymers of
AN-VI-AMSK alternatively Nafion perfluorinated type membranes have been
described in patents D.J.High - gate [49-52]. They have high proton
conductivity, adjustable hydrophilicity, ability to recycle the platinum catalyst
from the fuel cell and a low cost compared with membranes Nafion. The
disadvantage of such materials is their low mechanical strength in the hydrated
state, hindering the operation of polyelectrolytes in fuel cells operating at high
temperatures.
To improve the mechanical strength of the net ionic copolymers described
have implemented a grid of non-ionic copolymer of AN-CAP, thereby forming
a coherent CHD [47, 48]. By varying the ratio used in the synthesis of the
second grid and AM AN monomers and the weight ratio of grids can be adjusted
within wide limits water retention and mechanical properties of the resulting
IPN. The method allows to obtain the ion-exchange membrane having a
sufficiently high proton conductivity and mechanical strength in the hydrated
state at elevated temperatures (90 °C). It has been found that to maintain the
mechanical strength at elevated temperatures, the second polymer network
should be at least 10-15
%
of the original weight of the ionic polymer network.
It was found that such PRT have high proton conductivity than the initial
ionic copolymers produced in accordance with [49]. By - Apparently, the
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