Preparation and Performance Study of HTPB-g-(PNIPAM/PEG) Thermoresponsive Polymer Brush.

In recent years, a great deal of work has been devoted to the development of thermoresponsive polymers that can be made into new types of smart materials. In this paper, a branched polymer, HTPB-g-(PNIPAM/PEG), with polyolefin chain segments as the backbone and having polyethylene glycol (PEG) and poly(N-isopropylacrylamide) (PNIPAM) as side chains was synthesized by ATRP and click reactions using N3-HTPB-Br as the macroinitiator. This initiator was designed and synthesized using hydroxyl-terminated polybutadiene (HTPB) as the substrate. The temperature-responsive behavior of the branched polymer was investigated. The lower critical solution temperature (LCST) of the branched polymer was determined by ultraviolet and visible spectrophotometry (UV-vis) and was found to be 35.2 °C. The relationship between the diameter size of micelles and temperature was determined by dynamic light scattering (DLS). It was found that the diameter size changed at 36 °C, which was nearly consistent with the result obtained by UV-vis. The results of the study indicate that HTPB-g-(PNIPAM/PEG) is a temperature-responsive polymer. At room temperature, the polymer can self-assemble into composite micelles, with the main chain as the core and the branched chain as the shell. When the temperature was increased beyond LCST, the polyolefin main chain along with the PNIPAM branched chain assembled to form the nucleus, and the PEG branched chain constituted the shell.

Xanthene-based Hg2+ fluorescent probe for detection of Hg2+ in water/food samples, as well as imaging of live cells, zebrafish and tobacco seedlings.

In this paper, an Hg2+ detection probe, HOS, was prepared with a xanthene as the parent fluorophore. Hg2+-initiated thioacetal deprotection reaction is the detection mechanism of this probe. After testing, the probe HOS was able to accurately determine Hg2+ with a detection limit of 36 nM. It was successfully applied to the detection of Hg2+ in different water samples and shrimp samples, meanwhile, the filter paper strips prepared by HOS were obviously changed from light yellow to dark yellow under daylight, and from green to yellow under 365 nm UV light. Furthermore, probe HOS enabled Hg2+ bioimaging experiments on HepG2 cells, zebrafish and tobacco seedlings under laser confocal microscopy.

Synthesis and Comparative Study of Polyether-b-polybutadiene-b-polyether Triblock Copolymers for Use as Polyurethanes.

In this paper, the effects of HTPBs with different main-chain microstructures on their triblock copolymers and polyurethane properties were investigated. Three polyether-modified HTPB triblock copolymers were successfully synthesized via a cationic ring-opening copolymerization reaction using three HTPBs with different microstructures prepared via three different polymerization methods as the macromolecular chain transfer agents and tetrahydrofuran (THF) and propylene oxide (PO) as the copolymerization monomers. Finally, the corresponding polyurethane elastomers were prepared using the three triblock copolymers as soft segments and toluene diisocyanate (TDI) as hard segments. The results of an analysis of the triblock copolymers showed that the triblock copolymers had lower viscosity and glass transition temperature (Tg) values as the HTPB 1,2 structure content decreased, although the effect on the thermal decomposition temperature was not significant. An analysis of the polyurethane elastomers revealed that as the content of the 1,2 structure in HTPB increased, its corresponding polyurethane elastomers showed a gradual increase in breaking strength and a gradual decrease in elongation at break. In addition, PU-1 had stronger crystallization properties compared to PU-2 and PU-3. However, the differences in the microstructures of the HTPBs did not seem to have much effect on the surface properties of the polyurethane elastomers.

A multi-modal probe for trace water and simultaneously monitoring lipid droplets and lysosomes.

Recently, multifunctional fluorescent probes have received more and more attention with the rapid development of fluorescence imaging technology. In this article, a multifunctional fluorescent probe NAP-OH was designed and synthesized. NAP-OH exhibited outstanding polarity-sensing performance and was used to detect trace water in different organic solvents by means of fluorescence emission intensity. The fluorescence spectroscopy results indicated that NAP-OH was highly responsive to trace water in acetone (LOD = 28 ppm). The co-localization experiment and cell starvation imaging showed that the probe NAP-OH could be used to distinguish lysosomes from lipid droplets, showing bright red fluorescence in lipid droplets and weak red fluorescence in lysosomes. The oleic acid stimulation experiment shows that the probe can detect the dynamic changes of lipid droplets while observing lysosomes. In addition, NAP-OH showed great photostability and low cytotoxicity and was successfully used in zebrafish imaging. Therefore, these results indicated that NAP-OH, as a multifunctional fluorescent probe, would be used in trace water detection and biological imaging.

Preparation of oxime compound lipid droplet-specifically labeled fluorescent probe and its application in cell imaging.

Fluorescent probes can facilitate our further comprehension of the functional and physiological roles of LDs and thus promote the development of effective therapeutic approaches. Oxime compounds are widely used due to their good crystallinity and high reactivity. However, the majority oximes fluorescent probes are usually employed for the detection of HCIO, and the application of oximes in fluorescently labeled LDS is poorly reported. In this paper, three kinds of LDs fluorescent probes (NAP-a, NAP-b and NAP-c) with D-π-A structure were synthesized by simple synthesis method with 1,8-naphthalimide as fluorescent matrix and oxime group as electron donor. These probes were highly sensitive to polarity, and possessed good photostability and low cytotoxicity. Co-staining experiments showed that these probes could target LDs and the fluorescence image was green. These probes NAP-a, NAP-b and NAP-c possessed high Pearson coefficient (HeLa cells: 0.91, 0.95, 0.86) and Manders coefficient (HeLa cells: 0.91, 0.96, 0.86) with Nile Red. Interestingly, the dynamic variations in their size, shape and distribution could be clearly observed in the oleic acid-treated cell model of LDs. Imaging of zebrafish was performed and green fluorescence was collected in zebrafish. These excellent properties make oxime compound fluorescent probes a promising fluorescent probes for studying LDs and metabolic diseases. This study opens up a new way for the preparation of LDs fluorescent probe.

Smart Composite Hydrogels with pH-Responsiveness and Electrical Conductivity for Flexible Sensors and Logic Gates.

Stimuli-responsive conductive hydrogels have a wide range of applications due to their intelligent sensing of external environmental changes, which are important for smart switches, soft robotics, and flexible sensors. However, designing stimuli-responsive conductive hydrogels with logical operation, such as smart switches, remains a challenge. In this study, we synthesized pH-responsive conductive hydrogels, based on the copolymer network of acrylic acid and hydroxyethyl acrylate doped with graphene oxide. Using the good flexibility and conductivity of these hydrogels, we prepared a flexible sensor that can realize the intelligent analysis of human body motion signals. Moreover, the pH-responsive conductive hydrogels were integrated with temperature-responsive conductive hydrogels to develop logic gates with sensing, analysis, and driving functions, which realized the intellectualization of conductive hydrogels.

A novel synthetic strategy for styrene-butadiene-styrene tri-block copolymer with high cis-1,4 units via changing catalytic active centres.

A styrene-butadiene-styrene tri-block copolymer (SBS) with a high cis-1,4 unit content (greater than 97%) was synthesized by a novel synthetic strategy based on changing the catalytic active centres using n-butyllithium and a nickel-based catalyst. Firstly, styrene was polymerized via anionic polymerization using butyllithium as the initiator (Li, activity centre Li) at 50°C. The obtained alkylated macroinitiator (PSLi) was aged with nickel naphthenate (Ni) and boron trifluoride etherate (B) to prepare a second reactive centre (Ni-F), which was used to initiate the polymerization of butadiene (Bd). Finally, triphenyl phosphine (PPh3) was added to adjust the electron density of the third active centre (P-Ni-F), and styrene monomer was added again to synthesize the second polystyrene block to obtain SBS. The polymerization technique presented here is simple and has an efficient initiation effect due to the high initiation activities for the different monomers. It also exhibits excellent control over the stereo-structure of the butadiene segments in the prepared copolymers, and the SBS polymers with high cis-1,4 unit content were easily achieved.

Synthesis of Novel pH-Tunable Thermoresponsive Hydroxyl-Terminated Hyperbranched Polyether.

In this study, a new pH-tunable thermoresponsive hydroxyl-terminated hyperbranched polyether (HTHP 2) was successfully prepared via a one-pot cationic polymerization technique and postmodification. In the first step, hydroxyl-terminated hyperbranched polyether containing double bonds (HTHP 1) were synthesized. Then, through thiol-ene "click" reaction, pH-responsive carboxyl groups were introduced to the target polymer of HTHP 2. The products were characterized via Fourier-transform infrared spectra (FTIR), nuclear magnetic resonance (NMR), and size-exclusion chromatography-multiangle laser light scattering (SEC-MALLS). Moreover, dynamic light scattering (DLS) and UV-Vis spectroscopy was employed to study the pH- and thermoresponsiveness in detail. Results showed that HTHP 2 possessed typical pH-controllable thermoresponsive behavior. By regulating the solution pH value range 3.0-5.4, LCST of HTHP 2 could be changed from 12.8 to 68.0 °C. Meanwhile, the cell viabilities of A549 cells were more than 80% for in vitro cytotoxicity tests of HTHP 2, suggested that HTHP 2 polymers are of good biocompatibility for up to 24 h.

A New Strategy to Synthesize α,ω-Dihydroxy Multiblock Copolymers via [CpRu(CH3 CN)3 ]PF6 /Quinaldic Acid Catalyst.

In this study, a new strategy to synthesize random and alternating multiblock copolymers (MBCs) by the polycondensation of macromonomers' terminal hydroxyl groups with [CpRu(CH3 CN)3 ]PF6 /quinaldic acid as the catalyst is reported, which is often used for the preparation of a variety of biological small molecules via the reaction of allyl ethers. The degrees of hydroxyl functionality (Fn ) of the MBCs are assessed by titration, and the presence of hydroxyl on both the ends of MBCs is also confirmed by a chain-extension experiment of the ring-opening polymerization of D,L-lactide.

A New Synthesis Strategy on Styrene-Butadiene Di-Block Copolymer Containing High cis-1,4 Unit Via Transfer of Anionic to Coordination Polymerization.

A novel synthesis strategy on styrene-butadiene di-block copolymer (PS-b-PB) with high cis-1,4 unit content was developed, based on a transfer technique from anionic to coordination polymerization. Firstly, the styrene monomer was initiated by n-butyllithium (Li) utilizing anionic polymerization at 50 °C, which resulted in a macromolecular alkylating initiator (PSLi). Secondly, PSLi was aged with nickel naphthenate (Ni) and boron trifluoride etherate (B) for obtaining a complex catalyst system (Ni/PSLi/B). Then, Ni/PSLi/B was applied to initiate the butadiene (Bd) polymerization. Following this new strategy, a series of PS-b-PBs were successfully synthesized. The experimental results indicated that under the molar ratio combination of [Li]/[Ni] = 5 and [B]/[Li] = 1, styrene-butadiene di-block copolymers could be easily achieved with high cis-1,4 unit content (>97%) and controlled molecular weight as well as narrow molecular weight distribution (Mw/Mn < 1.5). Furthermore, the copolymer's block ratio could also be effectively controlled by controlling the two components' monomer feed ratio.

Synthesis and Properties of Side-Chain Functionalized Polytetrahydrofuran Derivatives via the Blue-Light Photocatalytic Thiol-Ene Reaction.

A series of side-chain functionalized polytetrahydrofuran (PTHF) derivatives were synthesized via the blue-light photocatalytic thiol-ene "click" reaction. Firstly, unsaturated polytetrahydrofuran (UPTHF) as a new unsaturated polyether was synthesized via condensation polymerization of cis-2-butene-1,4-diol and trans-1,4-dibromo-2-butene using potassium hydroxide (KOH) as a catalyst. Then, double bonds in the backbone of UPTHF were modified into different pendant functionality side groups by blue-light photocatalytic thiol-ene "click" reaction using Ru(bpy)3Cl2 as a photoredox catalyst, obtaining different side-chain functionalized PTHF derivatives. The structure and the morphology of the side-chain functionalized PTHF derivatives was characterized via Fourier-transform infrared spectra (FTIR), nuclear magnetic resonance (NMR), size exclusion chromatography/multi-angle laser light scattering (SEC/MALLS), and differential scanning calorimeter (DSC). The results showed that the blue-light photocatalytic thiol-ene reaction exhibited high efficiency, and all the unsaturated bonds were modified. Different branch units bestowed different performance of PTHF derivatives; we systematically investigated the thermal properties, pH-triggered and temperature-triggered, self-assembly behaviors of different PTHF derivatives.

Synthesis of high cis-1,4 polybutadiene with narrow molecular weight distribution via a neodymium-based binary catalyst.

This work explores the synthesis of polybutadiene (PB) with high cis-1,4 unit content and narrow molecular weight distribution using a neodymium-based complex, consisting of neodymium(iii) trifluoromethane sulfonate (Nd(CF3SO3)3) and coordinated with tris(2-ethylhexyl)phosphate (TOP). The complex's composition and structure are characterized by elemental analysis, XPS and FT-IR. Combined with Al(i-Bu)3, a binary catalyst is obtained and then applied to initiate the polymerization of butadiene. Results indicate that the catalyst system displays a high catalyst activity and the product polymer (PB) features a high cis-1,4 content (98.8%) and a remarkably narrow molecular weight distribution (M w/M n = 1.32). Compared with PB initiated by the current well-studied catalyst Nd(CF3SO3)3*3TBP/Al(i-Bu)3, the Nd(CF3SO3)3*3TOP allows significantly narrowing the molecular weight distribution of the PB, because the Nd(CF3SO3)3*3TOP is more easily dissolved in hexane. Therefore, butadiene was polymerized in a homogenous system and each monomer's polymerization was initiated in the single molecular state.