Visible Light-Induced Plasticity of Shape Memory Polymers

Polydiacetylene-Polyurethane Crisscross Elastomer as an Intrinsic Shape Memory Conductive Polymer

Owing to the high phase transition temperature and incompatibility with thermoplastic elastomers, conjugated polymers are hardly formulated as shape memory materials. This work presents a crisscross polymer composed of polyurethane and polydiacetylene. Phase separation is completely avoided based on the photoinduced polymerization of polydiacetylene from polyurethane chains. The two backbones are intercrossed and covalently linked to each other. Particularly, polyurethane acts as a soft segment to provide elastic performance, and the rigid polydiacetylene provides conductive pathways. Such a crisscross topology, combined with soft and rigid compositions, renders the possibility to serve the polymer as an intrinsically elastic conductive polymer. Intriguingly, the polymer possesses shape memory performance, meanwhile retaining the reliable conductivity. Electrical tests demonstrate that the shape memory conductive polymer is one attractive candidate for exploiting shape-customized strain sensors.

Surface Modification Based on Diselenide Dynamic Chemistry: Towards Liquid Motion and Surface Bioconjugation

Surface modification is an important technique in fields, such as, self-cleaning, surface patterning, sensing, and detection. The diselenide bond was shown to be a dynamic covalent bond that can undergo a diselenide metathesis reaction simply under visible light irradiation. Herein we develop this diselenide dynamic chemistry into a versatile surface modification method with a fast response and reversibility. The diselenide bond could be modified onto various substrates, such as, PDMS, quartz, and ITO conductive film glass. Different functional diselenide molecules could then be immobilized onto the surface via diselenide metathesis reaction. We demonstrated that by using this modification method we could achieve liquid motion in a capillary tube under light illumination. We also show that this approach has the potential to serve as an efficient modification method for surface bioconjugation, which has practical applications in clinical usage.

Water-induced poly(vinyl alcohol)/carbon quantum dot nanocomposites with tunable shape recovery performance and fluorescence

Water-induced shape memory polymers (SMPs) show promising applications in biomedicine, biosensing, anti-counterfeiting and intelligent actuating systems. However, the dual function of shape morphing and color switching has not been achieved in the water-induced SMP system. Herein, a novel water-induced SMP with both color-switching fluorescence behavior and shape memory performance is reported. The material is fabricated by crosslinking poly(vinyl alcohol) (PVA) and pH-responsive fluorescent carbon quantum dots (CQDs). The incorporation of CQDs with PVA not only improves the shape recovery performance but also endows the material with color-switching features. To our best knowledge, such smart ability is first realized in this PVA/CQD SMP system, and this report provides a novel strategy for fabricating smart water-induced SMPs with adjustable shape recovery performance and fluorescence.

Well-Defined Selenium-Containing Aliphatic Polycarbonates via Lipase-Catalyzed Ring-Opening Polymerization of Selenic Macrocyclic Carbonate Monomer

The synthesis of well-defined, biodegradable selenium-containing polymers remains a formidable challenge in polymer chemistry. Herein, a selenic cyclic carbonate dimer monomer (M_Se) was developed to generate well-defined, biodegradable aliphatic polycarbonates with selenide functionality on the backbone. The monomer was synthesized via the intermolecular cyclization of di(1-hydroxyethylene) selenide and diphenyl carbonate with lipase CA as catalysts in a mass of anhydrous toluene with very dilute monomer concentration. Then living ring-opening polymerization (ROP) was executed by solution method using the same lipase CA as catalysts. Similarly, the copolymerizations with commercial trimethylene carbonate (TMC) generated random copolymers demonstrated by ¹³C NMR, regulating the density of selenium functional groups. The resulting polymers exhibited a living polymerization characteristic, as evidenced by polymerization kinetics, predictable molecular weights, narrow molecular-weight distribution, and controlled copolymer compositions. Using hydrophilic macroinitiators (PEG), amphiphilic di/triblock copolymers could be obtained, suggesting their potential as controlled drug delivery system (DDS) and hydrogel scaffolds for tissue engineering.

Acid-Induced Multicolor Fluorescence of Pyridazine Derivative

Smart luminescent materials that are responsive to external stimuli have received considerable attention. Here, we report a new D-A type 1,2-pyridiazine derivative (3,4,5,6-tetrakis(4-methoxyphenyl)pyridazine (TPP)) exhibiting turn-on fluorescence upon acid exposure both in solution and in the solid state. The protonation of the 1,2-pyridiazine ring caused a variation in the emission colors of the acidification species from blue (406 nm) to orange-red (630 nm) with a huge Δλ_em (224 nm). As a result, a synthetic rainbow of emission in solution could be achieved from one single molecule, and white photoluminescence was readily tuned by controlled protonation. A trifluoroacetic acid (TFA)-sensor film made from TPP was demonstrated as a TFA-sensitive surface with high sensitivity and reversibility. On the basis of these findings, we constructed a solid-state TPP film with a photoacid generator and demonstrated data encryption and decryption via a cascade protonation reaction that was well controlled by UV light.

Dynamic diselenide-containing polyesters from alcoholysis/oxidation of γ-butyroselenolactone

A versatile protocol for the synthesis of a variety of multiresponsive diselenide-containing polyesters was investigated.