(13.) L'Alloret, Florence; Dispersions Stabilized at Temperatures of From 4 to 50 Degrees Celsius by Means of a Polymer Comprising Water-Soluble Units and Units with an LCST
; US Patent 7,652,100, Jan.
have demonstrated that in polymer blends, both spinodal and binodal temperatures can be determined through tracking the evolution of G' and G" in the dynamic temperature sweep test for both LCST
and upper critical solution temperature upper critical solution temperature (UCST) systems [59,60].
Only 5 mol% of o-NB moieties will decrease the LCST
of the block copolymer below 10[degrees]C, and the more o-NB groups there are the lower LCST
the block copolymer exhibits .
The pore sizes in the membranes show an effective change in pore diameters of ~70 nm (stdev 8nm) changing from an open pore in the collapsed state of 350 nm to a diameter of 280 nm in the hydrated state below the LCST
The values of the LCST
of the hydrogels were found by the first derivatives of the curves in Fig.
The solution of the random copolymer was found to show LCST
at 22[degrees] C in 0.1 M [Na.sub.2]S[O.sub.4], and the LCST
value increased to 33[degrees]C with increasing concentration of L-ascorbic acid because of the reduction of the TEMPO moieties (Figure 3(a)).
In late stage of gelation, particle size showed no response to changed temperature below the LCST
(Figure 4(b)) and stabilized around 30 nm, which is just slightly higher than the size distribution during the early stage at 25[degrees]C.
P(NIPAAm-co-AAm) and p(NIPAAm-co-AAm)/XA hydrogels that contain crotonic acid (CA) exhibit a lover critical solution temperature (LCST
) at 28[degrees]C, whereas p(NIPAAm-ce;-AAm)/IA, and P(NIPAAm-co-AAm)/ACA hydrogels exhibit a lover critical solution temperature at 30.7[degrees]C and 34.4[degrees]C, respectively.
A widely recognized mechanism to explain the LCST
behavior of PNIPAAm hydrogels was that the phase transition resulted from a balance between hydrophilicity and hydrophobicity in the polymeric backbone.
Also, it shows a lower critical solution temperature (LCST
) in the range of 30-50[degrees]C.
When the permeating temperature was below the LCST
of the PNIPAAm (around 32[degrees]), the PNIPAAm chains on the pore surfaces can be assumed a highly extended conformation, leading to a reduction in the effective pore size.
As the thennoresponsive PNIPAM can change their hydrophilic or hydrophobic behavior around the lower critical solution lemperaiure (LCST