For example, poly-N-isopropylacrylamide becomes insoluble at about 37[degrees]C, hydroxypropyl cellulose separates at temperatures above about 40[degrees]C and poloxamers gel once the temperature reaches the lower critical solution temperature (LCST
PVME is a water soluble polymer with a (LCST
) around 35[degrees]C and has the ability to form nanogel when its polymer solution at low concentrations and temperatures below LCST
(when molecules are well separated) is irradiated [20,21,42].
showed, in the same article, that by adding NIPA in one shot and an initiator (potassium persulfate) at 70[degrees]C, the NIPA polymerized and because the reaction temperature was higher than the LCST
of the PNIPA, it became hydrophobic and, as a consequence, migrated to the micellar core.
The result indicated that, as shown in Scheme 1, when the upconverting hybrid nanoparticles were irradiated by NIR light, the UCNPs converted NIR to UV light to induce the photocleavage reaction of NBA moieties in situ; then, as a result of the LCST
change of the block copolymers, nanoparticles disintegrated and released the loaded NR molecules.
A similar strategy has been applied to the deposition of sunscreens from aqueous solutions by synthesizing water-soluble polymers containing cinnamidoalkylamines and/or benzamidoalkylamines that have a lower critical solution temperature (LCST
) of 30[degrees]C or above and cationic groups for enhanced substantivity.
Measurements of cloud point were used to determine the phase separation temperature (i.e., LCST
, which is generally defined as the cloud point) of the casting solution, and the cloud point was measured by a self-made device .
For the grafted membranes, we were able to achieve very low flow rates with an upper limit in the order of 1 [micro]L/s [cm.sup.2] when the PNIPAM is below the LCST
. This indicates that the polymer below the LCST
is able to achieve nearly total blockage of the pores to convective flow.
For the temperature dependent swelling studies (to determine LCST
values), hydrogels were swollen in universal buffer (pH = 3.0 and pH = 8.0) at various temperatures (20-45[degrees]C).
The random copolymer, poly(TEMPMA-ran-NIPAAm), showed thermoresponsivity, and its lower critical solution temperature (LCST
) was observed at 31[degrees] C, which was slightly increased to 33[degrees] C after oxidation of tetramethylpiperidine moieties (Figure 2(a)).
SF/PNIPAAm composite hydrogel yielded transparence and achromaticity (Figure 1(a)) below the LCST
of PNIPAAm due to the additional PNIPAAm which interacts with SF and restrain SF aggregation and transition into cross-sheet dominated heterogeneous complex.
It is well known that the mixture of epoxy precursor and PES exhibits a lower critical solution temperature (LCST
) phase behavior , including the following: the hardener changes the polarity of the mixture and thus makes the phase decomposition follow a reaction-induced phase separation process, in which the homogenous mixture separates into two phases after the cloud point (with specific curing conversion).
A very well known temperature sensitive hydrogel is crosslinked poly(/V-isopropyl acrylamide) which has a lower critical solution temperature (LCST
) at 31-33[degrees]C in water [1, 2).