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Query: UMLS:C0344329 (collapse)
 28,634 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

This paper deals with a thermo-responsive poly(N-isopropylacrylamide) (NIPA) gel containing a polymeric surfactant poly(2-(methacryloyloxyl)decylphosphate) (PMDP) which shows rapid volume change above phase transition temperature at ca. 34 degrees C. Based on the measurements of dye-solubilization, it was suggested that intra-molecular micelles of the polymeric surfactant PMDP are inside NIPA gel-network. It is concluded that the intra-molecular micelles of polymeric surfactant involving NIPA chains may play crucial role in the rapid collapse of the NIPA-PMDP gel at the phase transition temperature.
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PMID:Thermo-responsive poly(N-isopropylacrylamide) gel containing polymeric surfactant poly(2-(methacryloyloxyl)decylphosphate): correlation between rapid collapsing characters and micelles of polymeric surfactant. 1853 10

Temperature-sensitive poly(N-isopropylacrylamide) (PNIPA) nanohydrogels were synthesized by nanoemulsion polymerization in water-in-oil systems. Several cross-linking degrees and the incorporation of acrylic acid as comonomer at different concentrations were tested to produce nanohydrogels with a wide range of properties. The physicochemical properties of PNIPA nanohydrogels, and their relationship with the swelling-collapse behaviour, were studied to evaluate the suitability of PNIPA nanoparticles as smart delivery systems (for active packaging). The swelling-collapse transition was analyzed by the change in the optical properties of PNIPA nanohydrogels using ultraviolet-visible spectroscopy. The thermodynamic parameters associated with the nanohydrogels collapse were calculated using a mathematical approach based on the van't Hoff analysis, assuming a two-state equilibrium (swollen to collapsed). A mathematical model is proposed to predict both the thermally induced collapse, and the collapse induced by the simultaneous action of two factors (temperature and pH, or temperature and organic solvent concentration). Finally, van't Hoff analysis was compared with differential scanning calorimetry. The results obtained allow us to solve the problem of determining the molecular weight of the structural repeating unit in cross-linked NIPA polymers, which, as we show, can be estimated from the ratio of the molar heat capacity (obtained from the van't Hoff analysis) to the specific heat capacity (obtained from calorimetric measurements).
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PMID:Temperature- and pH-sensitive nanohydrogels of poly(N-Isopropylacrylamide) for food packaging applications: modelling the swelling-collapse behaviour. 2452 Mar 26