Triggered cross-linking temperature

Examples of triggered cross-linked hydrogels. (a)Temperature, pH, and light-triggered sol-gel transition, (b) Polymeric chains with grafted antibodies are cross-linked in the presence of specific antigens, (c) Polymeric chains with immobilized RGD are cross-linked in the presence of cells. 

In the second chemical category, permanent shape is set by chemical cross-links formed during processing but a temporary shape is formed when the sample is deformed above the melting temperature of the crystalline components and subsequently cooled below this temperature (Liu et al., 2(X)7). Other than thermal heating, recovery in these SMPs can be triggered by an electric current at low voltage. Liquid... 

Shape memory polymers basically have two structural features—that is, the cross-links that determine the permanent shape and the reversible segments acting as a switching phase. Molecular mechanisms describing thermally triggered shape memory process are shown in Figure 4.1. In the figure, is the thermal transition temperature of the reversible phase... 

SMP based on miscible blends of semicrystalline polymer/amorphous polymer was reported by the Mather research group, which included semicrystalline polymer/amorphous polymer such as polylactide (PLA)/poly vinylacetate (PVAc) blend [21,22], poly(vinylidene fluoride) (PVDF)/PVAc blend [23], and PVDF/polymethyl methacrylate (PMMA) blend [23]. These polymer blends are completely miscible at all compositions with a single, sharp glass transition temperature, while crystallization of PLA or PVDF is partially maintained and the degree of crystallinity, which controls the rubbery stiffness and the elasticity, can be tuned by the blend ratios. Tg of the blends are the critical temperatures for triggering shape recovery, while the crystalline phase of the semicrystalline PLA and PVDF serves well as a physical cross-linking site for elastic deformation above Tg, while still below T ,. 

TEMPO is disproportionated into the OA and the AA by the acids [46]. The disproportionation of TEMPO also promoted the micellization of the PVTEMPO-i-PSt copolymer [51]. The series of micellizations using the TEMPO redox systems indicate that the electron transport becomes a trigger that causes self-assembly of molecules, in addition to external triggers such as temperature, pressure, pH, salt formation, and noncovalent bond cross-linking. 

Lee, S.Y., et al. Shell cross-linked polyethylenimine-modified micelles for temperature-triggered drug release and gene delivery. Rsc Advances 4(101), 57702-57708 (2014)... 

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