Three-dimensional structures that undergo reversible shape changes in response to mild stimuli enable a wide range of smart devices, such as soft robots or implantable medical devices. Herein, a dual thiol-ene reaction scheme is used to synthesize a class of liquid crystal (LC) elastomers that can be 3D printed into complex shapes and subsequently undergo controlled shape change. Through controlling the phase transition temperature of polymerizable LC inks, morphing 3D structures with tunable actuation temperature (28 ± 2 to 105 ± 1 °C) are fabricated. Finally, multiple LC inks are 3D printed into single structures to allow for the production of untethered, thermo-responsive structures that sequentially and reversibly undergo multiple shape changes.

Materials. Lithium chloride, lithium t-butoxide, isopropyl magnesium chloride (2M in THF), t-butyl magnesium chloride (2M in diethyl ether), n-butyl magnesium chloride (2M in THF), n-butyl lithium (1.6 M in hexane), and 9,9-dioctyl-2,7-dibromofluorene were purchased from Aldrich and used as received. Tetrahydrofuran was distilled from sodium benzophenone ketyl and collected over molecular sieves. n-Bu 3 MgLi was synthesized in anhydrous toluene at -10 0 C as previously reported.Synthesis of RMgCl.LiX (R = i-Pr or t-Bu; X = Cl or t-BuO). A dry 50 mL three-neck flask was flushed with nitrogen and was charged with a 2M solution of i-PrMgCl in THF (2.5 mL, 5 mmol) and 5 mL of anhydrous THF. Lithium salt (5 mmol) was added to the reaction flask under nitrogen. The reaction mixture was stirred for 6-8 hrs at room temperature.General synthesis of polymers using i-PrMgCl•LiCl as reagent for magnesium halogen exchange. A solution of dibrominated monomer (5 mmol) in 5 mL of anhydrous THF was added under nitrogen to the previously prepared solution of i-PrMgCl•LiCl (5 mmol). The reaction mixture was stirred at room temperature, and monitored by GC-MS.Analysis of the reaction mixture confirmed the formation of monoGrignard reagent in at least 85 % yield. Ni(dppp)Cl 2 (0.02 g, 0.04 mmol) was added to the reaction mixture dissolved in 10 mL anhydrous THF. The polymerization was allowed to proceed for 2-48 h at room temperature followed by quenching of the reaction mixture with methanol.The precipitated polymer was filtered through a thimble and subjected to methanol extraction. The polymer was dried under vacuum for 12 hrs.

This review describes the synthesis and photovoltaic performance of donor-acceptor (D-A) semiconducting polymers that have been reported during the last decade. 9,9-Dialkyl-2,7-fluorene, 2,7-carbazole,

A thermo-responsive poly{γ-2-[2-(2-methoxyethoxy)ethoxy]ethoxy-ε-caprolactone}-b-poly(γ-octyloxy-ε-caprolactone) (PMEEECL-b-POCTCL) diblock copolymer was synthesized by ring-opening polymerization using tin octanoate (Sn(Oct)(2)) catalyst and a fluorescent dansyl initiator. The PMEEECL-b-POCTCL had a lower critical solution temperature (LCST) of 38 °C, and it was employed to prepare thermally responsive micelles. Nile Red and Doxorubicin (DOX) were loaded into the micelles, and the micellar stability and drug carrying ability were investigated. The size and the morphology of the cargo-loaded micelles were determined by DLS, AFM, and TEM. The Nile-Red-loaded polymeric micelles were found to be stable in the presence of both fetal bovine serum and bovine serum albumin over a 72 h period and displayed thermo-responsive in vitro drug release. The blank micelles showed a low cytotoxicity. As comparison, the micelles loaded with DOX showed a much higher in vitro cytotoxicity against MCF-7 human breast cancer cell line when the incubation temperature was elevated above the LCST. Confocal laser scanning microscopy was used to study the cellular uptake and showed that the DOX-loaded micelles were internalized into the cells via an endocytosis pathway.

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