Jiaojun Tan

Fast and facile fabrication of porous polymer particles via thiol–ene suspension photopolymerization

A fast and facile method of preparing porous polymer particles via thiol–ene suspension photopolymerization was studied. The porous particles were fabricated by adding the porogen to the click chemistry system. In this paper, the photopolymerization of dipentaerythritol hexakis (3-mercaptopropionate), pentaerythritol tetrakis (3-mercaptopropionate), 1,3,5-tri-2-propenyl-1,3,5-triazine- 2,4,6(1H,3H,5H)-trione, sodium dodecyl sulfate, chloroform and different amounts of linear polymer porogen (polymethyl methacrylate, PMMA) was discussed in detail. The two crucial factors, polymerization time and amount of porogen, were investigated. It was demonstrated that the conversion of monomers could reach 80% within 15 s of irradiation, which further verified the high efficiency of click chemistry. By varying the amount of PMMA, we were able to tailor the particle size, pore diameters and morphology of the porous particles. Results of the mercury porosimetry indicated that the median pore diameter of particles was about 12.39 μm and the surface area was 4.393 m2 g−1. Moreover, the Tg of the particles given by DSC was about 45 °C.

Thiol–isocyanate click reaction in a Pickering emulsion: a rapid and efficient route to encapsulation of healing agents

An innovative, rapid and efficient route is developed to fabricate ene loaded microcapsules via a thiol–isocyanate click reaction based on a hydrolyzed poly(glycidyl methacrylate) (PGMA) particle stabilized oil-in-water Pickering emulsion. The whole process for the reaction only requires 10 min, opening up a new, time-saving and energy-efficient strategy. The oil droplets contain isophorone diisocyanate (IPDI), trimethylolpropane tris(3-mercaptopropionate) (TMMP) and 1,3,5-tri-2-propenyl-1,3,5-triazine-2,4,6 (1H, 3H, 5H)-trione (TTT), in which IPDI and TMMP are subsequently catalyzed by triethylamine (TEA) to produce a polythiourethane network, forming microcapsules. From scanning electron microscopy (SEM) and optical microscopy (OM), the resulting microcapsules are in good spherical shape and their outer surface is coated with a compact PGMA particle layer. The mean diameter of the TTT loaded microcapsules decreases from 238.8 to 110 μm with increasing the particle stabilizer concentration. Solid-state 13C NMR measurement proves that almost no side reactions exist in the base-catalyzed thiol–isocyanate reaction. Moreover, the core content (up to 67.8%) and the thickness of the shell wall (8–36 μm) can be adjusted by the feeding amount of core materials. These microcapsules with an outer PGMA layer disperse well and maintain their integrity in the epoxy coating, and no agglomeration is observed. Even though being encapsulated, the core ingredient maintains high reactivity as its raw version and exhibits favorable healing capability. Furthermore, besides TTT, the proposed method is versatile and applicable to the encapsulation of SR833S and diallyl phthalate.

Water-borne thiol–isocyanate click chemistry in microfluidics: rapid and energy-efficient preparation of uniform particles

A nucleophile-catalyzed thiol–isocyanate reaction has been exploited as an efficient route to fabricate uniform particles in a water-borne system. Droplets were generated in a simple microfluidic setup from stoichiometric thiol and isocyanate monomers, thereby creating an oil-in-water emulsion, and polymer particles were obtained once the monomer droplets were exposed to a nucleophile. This is the first report of thiol–isocyanate polymerization in a water-borne system, which shows great promise in the manufacture of particles for its mild conditions, rapid rate and high conversion. Notably, heat, UV, anhydrous or oxygen-free conditions are not required. It is demonstrated that particles with sizes ranging from 40 to 250 μm can be prepared via adjusting the flow rate of continuous and disperse phases. In addition, the functionality of the thiol monomer has a profound effect on the morphology of particles. This method opens up possibilities for nucleophile-catalyzed thiol–isocyanate click chemistry in water-borne and heterogeneous polymerization.

Synthesis and characterization of brush-like multigraft copolymers PnBA-g-PMMA by a combination of emulsion AGET ATRP and emulsion polymerization

In this paper, poly(n-butyl acrylate)-g-poly(methyl methacrylate) multigraft copolymers were synthesized by macromonomer technique and miniemulsion copolymerization. The PMMA macromonomers were obtained by an activator generated by electron transfer atom transfer radical polymerization (AGET ATRP) in emulsion system and subsequent allylation. Then the copolymerization of different macromonomers with nBA was carried out in miniemulsion system, obtaining multigraft copolymers with high molecular weight. The latex particles and distribution of emulsion AGET ATRP and miniemulsion copolymerization were characterized using laser light scattering. The molecular weight and polydispersity indices of macromonomers and multigraft copolymers were analyzed by gel permeation chromatography, and the number-average molecular weight range is 187,600-554,800 g/mol for PnBA-g-PMMA copolymers. In addition, the structural characteristics of macromonomer and brush-like copolymers were determined by infrared spectra and (1)H nuclear magnetic resonance spectroscopy. The thermal performance of brush-like copolymers were characterized by differential scanning calorimetry and thermogravimetric analysis. Atomic force microscopy results showed that the degree of microphase separation was varying with increasing PMMA content in PnBA-g-PMMA. The dynamic rheometer analysis revealed that multigraft copolymer with PMMA content of 31.4% exhibited good elastomeric properties to function as a TPE. These multigraft copolymers show a promising low cost and environmental friendly thermoplastic elastomer.

Facile fabrication of multihollow polymer microspheres via novel two-step assembly of P(St-co-nBA-co-AA) particles

A novel two-step assembly method was found and was used to fabricate special multihollow polymer microspheres. Firstly, monodisperse colloidal particles of poly(styrene-co-(n-butyl acrylate)-co-acrylic acid) (P(St-co-nBA-co-AA)) were synthesized by soap-free emulsion polymerization and the obtained emulsion was transferred to 1-octanol to form colloidosomes which were stabilized by Span 80 and the colloidal particles via assembling at the interface of water/oil. Secondly, the multihollow polymer microspheres were successfully fabricated by heat aggregation and fusion of the aforementioned colloidosomes and colloidal particles. The two-step assembly mechanism was revealed and explained based on the morphologies of multihollow polymer microspheres formed under different emulsifier amounts and sintering conditions.

Synthesis and characterization of graft copolymers PnBA-g-PS by miniemulsion polymerization

In this paper, poly(n-butyl acrylate)-g-poly(styrene) graft copolymers were synthesized by a macromonomer technique and miniemulsion copolymerization. The PS macromonomers were obtained by an activator generated by electron transfer atom transfer radical polymerization (AGET ATRP) in an emulsion system and subsequent allylation. Then the copolymerization of different PS macromonomers with nBA was carried out in a miniemulsion system, obtaining graft copolymers with different molecular weights. The latex particles and distribution of emulsion AGET ATRP were characterized using laser light scattering. The molecular weight and polydispersity indices of the macromonomers and graft copolymers were analyzed by gel permeation chromatography. In addition, the structural characteristics of the macromonomer and graft copolymers were determined by infrared spectra and 1H nuclear magnetic resonance spectroscopy. The thermal performance of the copolymers were characterized by differential scanning calorimetry and thermogravimetric analysis as compared with macroinitiators.

Fast magnetic-field-induced formation of one-dimensional structured chain-like materials via sintering of Fe3O4/poly(styrene-co-n-butyl acrylate-co-acrylic acid) hybrid microspheres

A facile and fast procedure has been developed to prepare one-dimensional (1D) hybrid microchains by sintering of Fe3O4/poly(styrene-co-n-butyl acrylate-co-acrylic acid) (Fe3O4/P(St-co-nBA-co-AA)) hybrid microspheres. Noteworthily, it is the first time that the 1D structure has been linked and fixed via physical fusion instead of by a chemical method. The crucial process is to sinter the hybrid microspheres at the glass transition temperature (Tg) of P(St-co-nBA-co-AA) particles under a magnetic field. SEM, optical microscopy, EDS, XRD and FTIR have proved the successful fabrication of 1D Fe3O4/P(St-co-nBA-co-AA) hybrid microchains and the formation mechanism has been discussed. The 1D hybrid microchains have lengths of several hundred micrometers and diameters of 10–15 μm. A TGA measurement has indicated that the large proportion of fused polymer particles in the 1D structures reaches 64.5%. A VSM curve has shown that the saturation magnetization is 18.7 emu g−1, which is enough for the 1D microchains to be controlled and separated by the external magnetic field. Mercury intrusion porosimetry and a SEM image of the fractured 1D microchains have demonstrated that these microchains are porous. Moreover, it has been found that individual microchains can be obtained at a low concentration of Fe3O4 particles, otherwise aggregation occurs.

Recyclable cross-linked hydroxythioether particles with tunable structures via robust and efficient thiol-epoxy dispersion polymerizations

The highly efficient base-catalyzed thiol-epoxy reactions were exploited in dispersion polymerizations as a simple method for the preparation of uniform and cross-linked particles with a tunable size, glass transition temperature (Tg) and network structure. Particles with sizes ranging from 1 μm to 3 μm could be obtained by varying monomer concentration and reaction medium, while the Tgs could be increased from −10 °C to 65 °C by adjusting the monomer functionality and structure. In order to further demonstrate the potential of these particles, the thioether bonds were simply oxidized to sulfoxides and sulfones to increase the Tgs and stiffness of the particles significantly. Moreover, the cross-linked particles proved to be reprocessable to a polymer material when a proper catalyst was incorporated. We believe that this simple and efficient method will become a powerful tool for particle preparation, and paves the way for polymer particle reinforcement and recycling.

Evaluation of thiol-ene photo-curable resins using in rapid prototyping

Purpose The purpose of this paper is to evaluate the properties of several thiol-acrylate photosensitive systems and compare with corresponding acrylate free-radical systems. The potential stereolithography applications of thiol–ene photosensitive systems are also discussed. Design/methodology/approach In the both thiol–ene and acrylate free-radical photosensitive systems, various key performances were characterized. The function group conversions were characterized by real-time Fourier transform infrared spectroscopy. The tension strength was determined according to the standard ASTM D638-2003, the flexible strength was determined according to ASTM D790-07 and the hardness was measured according to ASTM D2240-05. The volume shrinkage was measured by dilatometer method. The glass transition temperature was analyzed by differential scanning calorimeter. Findings As adding mercapto propionates into acrylate system, the inhibition of polymerization by oxygen was controlled and the flexible performance was improved. In addition, the photosensitive resin showed better tension strength, higher elongation at break and lower volume shrinkage. Among the four mercapto propionates, rigid TEMPIC showed most obvious affect, followed hexa-functional DPMP, tetra-functional PETMP and tri-functional TMMP. Originality/value Although the thiol–ene photosensitive resin has unmatched advantages in performance, there are no reports on the thiol–ene photosensitive resin in the stereolithography application. In this study, thiol–ene photopolymerization material was first tentatively implemented in stereolithography area. Several critical performance parameters were compared between thiol–ene and acrylate free-radical photosensitive systems.

Correction: Synthesis and characterization of graft copolymers PnBA-g-PS by miniemulsion polymerization

Correction for ‘Synthesis and characterization of graft copolymers PnBA-g-PS by miniemulsion polymerization’ by Hui Li et al., RSC Adv., 2015, 5, 45459–45466.