Thermo-responsive behavior of borinic acid polymers: experimental and molecular dynamics studies

Synthesis of New Glycine-Based Polymers and their Thermoresponsive Behavior in Water

In this work, new glycine-derived polymers are developed that exhibit thermoresponsive properties in water. Therefore, a series of monomers containing one, two, or three amide functional groups and one terminal cyanomethyl group is synthesized. The resulting homopolymers, obtained by free radical polymerization (FRP) and reversible addition fragmentation chain transfer (RAFT) polymerization, display a sharp and reversible upper critical solution temperature (UCST)-type phase transition in water. Additionally, it is shown that the cloud point (TCP) can be adjusted over more than 60 °C by the number of glycyl groups present in the monomer structure and by the polymer's molar mass. These novel thermoresponsive polymers based on cyanomethylglycinamide enrich the range of nonionic UCST polymers and are promising to find applications in various fields.

One-Pot Synthesis of Stimuli-Responsive Fluorescent Polymers through Polymerization-Induced Emission

Stimuli-responsive opposite emission (A)/absorption (B) polymer material (A∪B = Ω and A∩B = Ø) represents a novel polymer material that is difficult to prepare. Here, we demonstrate a one-pot strategy for the molecular design of stimuli-responsive opposite emission/absorption polymer material with intriguing properties of opposite emission/absorption and aggregation-induced emission (AIE) type nontraditional intrinsic luminescence (NTIL) in the visible region, through reversible addition-fragmentation chain transfer polymerization-induced emission (PIE) of the N,N-dimethyl-triphenylmethanol moiety. Investigations reveal that NTIL is due to the through-space conjugation effect caused by polymer chain entanglement, when increasing the repeating unit number. The corresponding stimuli-responsive opposite emission/absorption properties are derived from the carbocation-quinoid mechanism, which enables the fluorescence encryption capability. This work therefore demonstrates the proof of concept of a novel opposite emission/absorption polymer material that might cause inspiration in different fields.

Barbier single-atom polymerization induced emission as a one-pot approach towards stimuli-responsive luminescent polymers

A one-pot strategy for the design of stimuli-responsive luminescent polymers has been demonstrated through Barbier PIE, where the N,N-dimethyl moiety endows the polymers with both stimuli-responsive and red-shifted nonconjugated emission properties.

The effect of the degree of substitution on the solubility of cellulose acetoacetates in water: A molecular dynamics simulation and density functional theory study

The effect of the degree of substitution (DS) on the aqueous solubility of cellulose acetoacetates (CAA) was investigated by molecular dynamics simulations and density functional theory calculations. Using average non-covalent interaction and the electrostatic potential analyses done on cellobiose as the model, it was showed both polar and non-polar areas of the system increased as the more hydroxyls were replaced by acetoacetate groups. Analyses of the solvation free energies of a celludecose (glucan containing 10 monosaccharide sugar units) at constant pressure and temperature showed the polar solvation free energies and the number of decose-water hydrogen bonds increased as DS was varied from 0.3 to 0.8, which contributes to higher solubility in water. When the DS of CAA increased from 0.8 to 1.5, it became insoluble again because the plateaued increase in solvation free energy could no longer compensate for the decreasing CAA-water hydrogen bonding interactions. The growing van der Waals interactions among CAA molecules as the molecule grows bigger with each attached AA group also contributes to the decreasing water solubility.

Promoting water dissociation performance by borinic acid for the strong-acid/base-free hydrogen evolution reaction

Borinic acid is reported as a new proton donor with promoted water dissociation performance for the strong-acid/base-free hydrogen evolution reaction.

Thermo-responsive gels based on supramolecular assembly of an amidoamine and citric acid

In this work, we report the formation of a novel, aqueous-based thermo-responsive, supramolecular gelling system prepared by a convenient and efficient self-assembly of a long-chain amino-amide and citric acid. To determine the viscosity behavior and to gain insights into the gelation mechanism, a complementary combination of techniques, including Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), dynamic light scattering (DLS), and sinusoidal oscillatory tests, were used. The supramolecular gelator exhibited remarkably reversible sol-gel transitions induced by temperature at 76 °C. At a concentration of 5 wt%, the zero-frequency viscosity of the supramolecular system increased by about four orders of magnitude (from 4.2 to 12 563 Pa s) by changing the temperature from 23 °C to 76 °C. The viscous nature of the supramolecular gel could be preserved up to 90 °C. The synergistic combination of the hydrogen bonding between amino and carboxylic acid groups and the electrostatic interactions arising from the protonation of the amino-group and the deprotonation of carboxylic acid groups enhanced at higher temperatures is presumably responsible for the thermo-responsive behavior. We anticipate that these supramolecular gelators can be beneficial in various applications such as hydrogel scaffolds for regenerative medicine, personal care products and cosmetics, and enhanced oil recovery as viscosity modifiers.

The introduction of the Barbier reaction into polymer chemistry

The Barbier reaction, a widely utilized reaction for carbon-carbon bond formation, has played important roles in modern organic chemistry for more than a century. Here, we show its successful introduction to polymer chemistry. Through one-pot Barbier polyaddition (both A₂+B₂ type and AB type) of monomers containing an organic halide and a benzoyl group, a series of phenylmethanol group containing polymers, including polymonophenylmethanol (PMPM), polydiphenylmethanol (PDPM), and polytriphenylmethanol (PTPM), have been synthesized. Para-PTPM exhibits interesting aggregation-induced emission, tunable thermo-responsive over a wide temperature range, sensory, luminescence enhancement of fluorescent dye in solid-state and processing properties. This significantly expands the libraries of monomer and polymer, and opens up an avenue for the design and application of functional polymer materials.

Novel Ratiometric Fluorescent Nanothermometers Based on Fluorophores-Labeled Short Single-Stranded DNA

Novel ratiometric fluorescent short single-stranded DNA (ssDNA) nanothermometers (ssDNA FT) were developed using the fluorescence resonance energy transfer (FRET) effect of the ssDNA's end labeled fluorophores. An optimal ssDNA sequence and associated ssDNA FT were determined through combined MD simulation and temperature-related FRET analysis. Their fluorescence properties and thermo-responsivities were analyzed using fluorescence spectra. The influences of ssDNA' sequence length, sequence composition and fluorescent labels for temperature sensing were investigated. Results revealed the prepared, optimized ssDNA FT showed a high average temperature sensitivity of 7.04% °C^1-, wide linear response range of 0-100 °C, and excellent stability with various environmental factors. Furthermore, this ssDNA FT was successfully used for intracellular temperature sensing in cancer cells and was used for in vivo thermos-imaging during microwave hyperthermia of tumor tissue. Advantages in size, sensitivity, and stability proved the feasibility of ssDNA FT in nanoscale thermometry applications, and this novel fluorescent thermometry mechanism is of large potential in the development of FTs. This investigation of ssDNA's molecular thermosensitivity could give rise to a new prospective in the nanothermometry field.

Borinic Acid Polymer: Simplified Synthesis and Enzymatic Biofuel Cell Application

A simplified one-pot and less harmful method has been introduced for the synthesis of borinic acid monomer. The corresponding borinic acid polymer (PBA) has been prepared by reversible addition-fragmentation chain transfer polymerization. Property investigations confirm the characteristics of PBA as a new type of "smart material" in the field of thermo-responsive polymer. The potential application of PBA in the field of enzymatic biofuel cell has been illustrated with a wide open circuit potential of 0.92 V.

Functional micelles formed from glucose-, thermo- and pH-triple responsive copolymers for controlled release

Spherical micelles self-assembled from the block copolymer PPBDEMA-b-PDMAEMA presented glucose, thermo- and pH-triple responsive properties.

Rheological Study and Molecular Dynamics Simulation of Biopolymer Blend Thermogels of Tunable Strength

The temperature-induced gelation of chitosan/glycerophosphate (Chs/GP) systems through physical interactions has shown great potential for various biomedical applications. In the present work, hydroxyethyl cellulose (HEC) was added to the thermosensitive Chs/GP solution to improve the mechanical strength and gel properties of the incipient Chs/HEC/GP gel in comparison with the Chs/GP hydrogel at body temperature. The physical features of the macromolecular complexes formed by the synergistic interaction between chitosan and hydroxyethyl cellulose in the presence of β-glycerophosphate disodium salt solution have been studied essentially from a rheological point of view. The temperature and time sweep rheological characterizations of the thermogelling systems revealed that the sol-gel transition temperature of the Chs/HEC/GP blends is equal to 37 °C at neutral pH; with increasing HEC content in the solutions, more compact networks with considerably improved gel strength are formed without influencing the gelation time. The formed hydrogel matrix has enough mechanical integrity and adequate strength for using it as injectable in situ forming matrices for biomedical applications. The classical Winter-Chambon (W-C) and Fredrickson-Larson (F-L) theories were applied to determine the gel point. In view of the obtained results, it is shown that the F-L theory can be employed as a robust and less tedious method than the W-C approach to precisely determine the gel point in these systems. At the end, molecular simulation studies were conducted by using ab initio quantum mechanics (QM) calculations carried out on Chs and HEC models, and molecular dynamics (MD) simulations of solvated Chs/HEC blend systems showed the binding behavior of Chs/HEC polymers. Analyses of interaction energy, radial distribution function, and hydrogen bonding from simulation studies strongly supported the experimental results; they all disclosed that hydrogen-bond formation between Chs moieties with regard to HEC chains plays an important role for the stabilization of the complexes.

Thermo-responsive rheological behavior of borinic acid polymer in dilute solution

Borinic acid polymer is rheologically thermo-responsive in solution, which expands its application as a new type of “smart” polymer.