Jianwei Guo

Novel halogen-free flame retardants based on adamantane for polycarbonate

A novel series of flame retardants (FRs) containing phosphate moieties attached to a bridgehead-substituted adamantane, 1-(diphenyl phosphate) adamantane (DPAd), 1,3-bis(diphenyl phosphate) adamantane (BDPAd), 1,3,5-tris(diphenyl phosphate) adamantane (TDPAd) and 1,3,5,7-tetrakis(diphenyl phosphate) adamantane (TKDPAd), were systematically synthesized in an attempt to develop efficient FRs for polycarbonate (PC). Their chemical structures were confirmed by Fourier Transform Infrared Spectroscopy (FTIR), Nuclear Magnetic Resonance (1H and 31P NMR), elemental analysis and melting point measurements. The flame-retarding efficiencies of the FRs were evaluated by Limited Oxygen Index (LOI), UL-94 vertical burning experiments, Scanning Electron Microscopy (SEM), Cone Calorimeter Test (CCT), Thermogravimetric Analysis (TGA), FTIR and TGA-FTIR. For TKDPAd, thermal decomposition took place in a sharply two-step mechanism at high temperature above 381.5 °C. A significant improvement of flame-retardant performance in PC/TKDPAd among the PC/FR was observed with an addition of 8 wt% TKDPAd in the presence of an anti-dripping agent (0.1 wt%). High thermal stability and phosphorus content of flame retardant are believed to be of great importance for efficient flame-retardant action of adamantane-based phosphates.

Thermo-moldable self-healing commodity plastics with heat resisting and oxygen-insensitive healant capable of room temperature redox cationic polymerization

Commercially available polystyrene is coupled with self-healability by exploiting a novel healing chemistry of redox cationic polymerization. In this system, iodonium bis(4-methylphenyl) hexafluorophosphate (IBH)/glycidyl methacrylate (GMA) loaded microcapsules and NaBH4 particles are embedded in the matrix through compression molding. The healant is oxygen insensitive and heat resistant so that it meets the requirement of remendable thermoplastics.

Synthesis of Adamantane-Based Trimeric Cationic Surfactants

Abstract GRAPHICAL ABSTRACT

Fluorinated Porous Poly(spirobifluorene) Via Direct C‒H Arylation: Characterization, Porosity, and Gas Uptake

Considering intrinsic properties of conjugated polyfluorenes and special functions of porous polymers, synthesis of fluorinated porous poly(spirobifluorene) via direct C−H arylation polycondensation is explored. Owing to the contorted structure and cross-linking nature, the obtained polymer FPSBF shows permanent porosities with Brunauer–Emmett–Teller specific surface area up to 700 m2 g−1 and exhibits a narrow pore size distribution with the dominant pore size at about 0.63 nm, which is more suitable for adsorption of small gas molecules. Based on the measured gas physisorption isotherms with pressure up to 1.13 bar, the obtained polymer shows good uptaking capacities for hydrogen (1.30 wt% at 1.0 bar and 77 K) and methane (4.80 wt% 1.0 bar and 273 K). Moreover, FPSBF has significant adsorption selectivity for CH4 against N2 and the estimated ideal adsorption selectivity ratio is up to 30/1 at 1.0 bar and 273 K, which makes the material possess potential application in gas separation.

Synthesis, physiochemical property and antibacterial activity of gemini quaternary ammonium salts with a rigid spacer

A novel series of adamantane-based gemini quaternary ammonium salts (GQASs) named as m-Ad-m (bromides, alkyl chain length, m = 12, 14, 16) are synthesized from 1,3-adamantanedicarboxylic acid. Their chemical structures are confirmed by 1H NMR, FT-IR and ESI-MS. The surface activities in aqueous solutions of m-Ad-m are evaluated by surface tension. Unlike conventional GQASs with a flexible spacer, m-Ad-m possessing a rigid adamantane spacer show lower surface tension (γCMC) values as compared to conventional GQASs bearing the same alkyl chains. The thermodynamic properties of m-Ad-m are examined by electrical conductivity measurements at different temperatures, including molecular interaction parameters (β), standard Gibbs free energy (ΔG0m), enthalpy (ΔH0m) and entropy (ΔS0m), which show that the micellization of m-Ad-m is entropy-driven. TEM study exhibits that the aggregate morphologies of m-Ad-m change from micelles and spheroidal vesicles of varying size to network aggregates and then to globular vesicles with the increase in m-Ad-m concentration. Furthermore, the antimicrobial efficacy of m-Ad-m against both Gram-positive bacteria (S. aureus and B. subtilis) and Gram-negative bacteria (E. coli, P. aeruginosa and V. parahaemolyticus) is systematically studied by minimum inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) methods, which indicates the favorable antibacterial activity of 12-Ad-12 against the studied bacteria.

Synthesis of thermochemically stable tetraphenyladamantane-based microporous polymers as gas storage materials

In view of environmental pollution control and purification of natural gases, developing ideal porous materials for small gas molecule (hydrogen, methane and carbon dioxide) capture is an important, pressing challenge. Accordingly, herein, three microporous organic polymers (MOP-Ad) have been synthesized by Suzuki coupling polymerization of 1,3,5,7-tetrakis(4-bromophenyl)adamantane “knots” with three phenylboronic acid-type “rods”. Gas adsorption studies of the MOP-Ad materials demonstrated their permanent porosity and good gas storage capabilities (1.07 wt% H2 at 77.3 K and 1.13 bar, 10.3 wt% CO2 and 2.4 wt% CH4 at 273.1 K and 1.13 bar), as well as moderate CO2/CH4 adsorption selectivity. Moreover, high thermal stability (up to 520 °C) and remarkable chemical resistance to strong acids and bases were found in these polymers, making them suitable candidates as gas storage materials in harsh chemical environments.

Delivery of anticancer drug using pH-sensitive micelles from triblock copolymer MPEG-b-PBAE-b-PLA

To improve the drug release rate in well-controlled manner, a new pH-sensitive triblock amphiphilic copolymer methyl poly(ethylene glycol) ether-b-poly(β-amino esters)-b-poly lactic acid (MPEG-b-PBAE-b-PLA) and its self-assembled micelles were developed for anticancer drug delivery. The average molecular weight and molecular structure of MPEG-b-PBAE-b-PLA were confirmed by gel permeation chromatography (GPC) and 1H NMR. The formation of self-assembled micelles, the microstructures at different pH values, and the distribution of doxorubicin (DOX) were investigated by dissipative particle dynamics (DPD) simulation combined with experimental techniques. The copolymers formed stable core-shell-type micelles in water. The critical micelle concentration (CMC) values, particle sizes and zeta potentials of the blank micelles increased along with globule-extended conformational transitions when the pH values decreased from 7.4 to 5.0, due to the protonation of amine groups of PBAE. Obvious increases in the particle sizes and the drug loading content of micelles were observed with increasing DOX. The in vitro release behavior of DOX from the micelles was pH-dependent. The DOX release rate was improved obviously as pH decreased from pH7.4 to pH5.0, with over 96% of DOX was released within 48h. The drug release mechanism under different conditions was also analyzed using theoretical formulas. All the results suggest that the pH-sensitive MPEG-b-PBAE-b-PLA micelles might be a prospective candidate as anticancer drug delivery carrier with well-controlled release behavior.

Novel sulfonate-containing halogen-free flame-retardants: effect of ternary and quaternary sulfonates centered on adamantane on the properties of polycarbonate composites

In order to find a more environmentally friendly flame retardant, we have designed a novel halogen-free flame-retardant (FR) system consisting of ternary and quaternary sulfonates centered on adamantane. They are named 1,3,5-tri(phenyl-4-sodium sulfonate)adamantane (AS3) and 1,3,5,7-tetrakis(phenyl-4-sodium sulfonate)adamantane (AS4), respectively. Both kinds of FRs were synthesized and compounded with polycarbonate (PC) to study their effects on the properties of PC composites. The results show that the new FR system can improve PC flame retardancy efficiently, and has mechanical strength advantages as well. The PC composites with only 0.1 wt% AS3 or 0.08 wt% AS4 can pass vertical burning tests (UL-94) V-0 level, with increasing the value of limiting oxygen index (LOI) to 31.2% or 32.3%. Moreover, they can maintain ideal mechanical properties compared to neat PC simultaneously. Finally, the flame retardant mechanism of this system was verified via thermal analysis, morphology and chemical structure analysis of the char residues.

Synthesis of the polymerizable room temperature ionic liquid AMPS – TEA and superabsorbency for organic liquids of its copolymeric gels with acrylamide

A polymerizable room temperature ionic liquid (RTIL), 2-acrylamido-2-methyl-1-propane sulfonic acid (AMPS) – triethylamine (TEA), was synthesized by neutralization of AMPS with TEA in acetone followed by evaporation of the solvent under a reduced pressure at room temperature. The RTIL was characterized with fourier transform infrared spectroscopy, differential scanning calorimetry (DSC), and 1H NMR. Co-polymeric gels of the RTIL with acrylamide (AAm) were prepared by aqueous solution polymerization using N,N′-methylenebisacrylamide as a crosslinker, and ammonium persulfate as an initiator. Superabsorbency of the gels in aqueous and a series of organic liquids was investigated gravimetrically. DSC data showed that the glass transition temperature of AMPS – TEA was −59.4 °C. Poly(AMPS – TEA-co-AAm) gels exhibited superabsorbency in both water and a series of organic solvents. The mechanism for swelling in aqueous and organic media of the gels was critically discussed.

Fabrication of PDEAEMA-based pH-responsive mixed micelles for application in controlled doxorubicin release

Co-micellization of the diblock polymers poly(ethylene glycol) methyl ether-b-poly(N,N-diethylaminoethyl methacrylate) (MPEG–PDEAEMA) and poly(ethylene glycol) methyl ether-b-polycaprolactone (MPEG–PCL) was carried out to avoid the complicated synthetic steps of a single polymer and enhance the drug loading contents as well as the pH-responsive drug release performances of the polymers. The molecular weight and molecular structure of MPEG–PDEAEMA and MPEG–PCL were measured and confirmed by gel permeation chromatography (GPC) and 1H NMR. With the mass ratio of MPEG–PCL and MPEG–PDEAEMA set at 1 : 3, all three mixed micelles, MIX1 (MPEG–PCL40 and MPEG–PDEAEMA20), MIX2 (MPEG–PCL60 and MPEG–PDEAEMA35), and MIX3 (MPEG–PCL80 and MPEG–PDEAEMA50), showed good stability and excellent pH-responsive performances according to their critical micellar concentrations (CMC), particle sizes, and zeta potentials. The doxorubicin (DOX) loading content (LC) and entrapment efficiency (EE) of the micelles were 26.79% and 63.19% (MIX1), 22.81% and 59.03% (MIX2), and 21.46% and 54.65% (MIX3), respectively. As the PDEAEMA/PCL content increased, the drug loading content decreased, which was further confirmed by dissipative particle dynamics (DPD) simulations. The results indicate that the mixed micelles developed in this study might have some advantages in improving the drug loading capacity of the polymers. The drug release profiles demonstrate that the mixed micelles have excellent ability for the controlled release of DOX, suggesting great potential for application of the micellar systems in drug delivery, especially in the area of pH-targeted tumor treatment.