This is the first report about the ring-opening polymerization of thiolactide, which is the thioester analogue of lactide. The cyclic condensation of thiolactic acid gave rac-thiolactide, which ...underwent the ring-opening polymerization by a combination of thiol as the initiator and DBU as the catalyst. The polymerization was in equilibrium, showing that the monomer conversions were as low as 20% in solvents. The bulk polymerization at r.t. led the monomer conversions around 50%, and the molecular weights of the polymer products increased with decreasing the amount of the thiol initiator. The MALDI-TOF mass spectra revealed that the hexane-insoluble polythiolactide (Mn = 3000–3500, PDI = 1.3–1.6, 20–30%yield) had not only the linear but also the macro cyclic structures. A much weaker base, pyridine, worked as the catalyst, showing the lower activity but leading the polymerization to a more controllable fashion. DFT calculation suggested that rac-thiolactide has the smaller ring-strain than rac-lactide, which agreed with the lower polymerizability of rac-thiolactide. Polythiolactide showed the higher degradability for alkaline hydrolysis and UV photolysis than polylactide. Copolymerization of thiolactide with thioglycolide was also studied.
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•Thiolactide, the thioester analogue of lactide, undergoes ring-opening polymerization.•Thiol-amine combinations conduct the ring-opening polymerization of thiolactide.•The ring-opening polymerization of thiolactide proceeds in an equilibrium manner.•Polythiolactide is more sensitive for alkaline hydrolysis and UV degradation than polylactide.
Mechanical initiation of polymerization offers the chance to generate polymers in new environments using an energy source with unique capabilities. Recently, a renewed interest in mechanically ...controlled polymerization has yielded many techniques for controlled radical polymerization by ultrasound. However, other types of polymerizations induced by mechanical activation are rare, especially for generating high‐molecular‐weight polymers. Herein is an example of using piezoelectric ZnO nanoparticles to generate free‐radical species that initiate chain‐growth polymerization and polymer crosslinking. The fast generation of high amounts of reactive radicals enable the formation of polymer/gel by ultrasound activation. This chemistry can be used to harness mechanical energy for constructive purposes in polymeric materials and for controlled polymerizations for bulk‐scale reactions.
Sound polymerization: Reported is an example of using piezoelectric ZnO nanoparticles to generate free‐radical species that initiate chain‐growth polymerization and polymer crosslinking. The fast generation of high amounts of reactive radicals enabled the formation of a high‐molecular‐weight polymer/gel by ultrasound activation. TDA‐1=tris2‐(2‐methoxyethoxy)ethylamine.
In this article, the synthesis of four novel bioelastomers known as poly (xylitol sebacate) (PXS), poly (xylitol adipate) (PXA), poly (sorbitol sebacate) (PSS), and poly (sorbitol adipate) (PSA) was ...carried out through bulk polymerization, followed by their blending using the solution method. Six blends were prepared namely PXS25/PSS75, PXS50/PSS50, PXS75/PSS25, PXS50/PXA50, PSA50/PXA50, and PSS50/PSA50. After blending, a thermal curing process was applied to the samples. The intrinsic viscosity, density, Tg, hydrophilicity, degradation, wound healing, and mechanical properties of polymers and blends were measured to investigate the effects of blending. Analyzing hardness, modulus, stress at breakpoint, degradation, and hydrophilicity data showed that the mechanical properties of bioelastomers are adjustable by blending for tissue engineering. Furthermore, the scratch assay proved the biocompatibility of pure polymers and indicated that blending does not have a negative impact on this matter.
Synthesis, blending, and curing of poly (polyol sebacate) and poly (polyol adipate) bioelastomers.
•ICEMA is oxidized on positive AC electrode to form stable electropolymerized layer.•PICEMAs formed by EP and RP methods mitigate diffusion-controlled self-discharge.•Isocyanate of PICEMA stabilizes ...ionic charged state to suppress self-discharge.•PICEMA formed by EP method shows minimized deterioration of capacitance and impedance.•EP method is suitable for highly capacitive and self-discharge-suppressed cell.
To mitigate the self-discharge of supercapacitors (SCs), numerous researches have reported about the effective use of cell resistance, although this might provoke a deterioration of charge/discharge performances. In this work, isocyanate-based electrolytic additive, 2-isocyanatoethylmethacrylate (ICEMA), is polymerized by two methods, in-situ electropolymerization (EP) and radical-polymerization (RP), on activated carbon (AC) electrode to mitigate the diffusion-controlled self-discharge, which is a major contribution to the self-discharge herein. Although the radical-polymerized PICEMA reveals favorable suppression of self-discharge, only confined in bulk electrolyte and meso-region, this exhibits severe increases in all impedance parameters and deteriorated charge/discharge capabilities. The electropolymerized PICEMA, however, meets the bifunctional perspective, revealing aptly retained capacitance and suppressed self-discharge behavior throughout micro- and meso-regions. ICEMA is effectively electropolymerized on positive AC electrode at + 0.9 ~ 1.2 V (vs. AC), which is confirmed by the electrochemical impedance spectroscopy, electrochemical quartz microbalance, and X-ray photoelectron spectroscopy. The functionality of isocyanate group to suppress self-discharge is also confirmed by comparing methoxy group of ethylene glycol methyl ether methacrylate (EGMEMA).
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•A AgNPs- based colorimetric/SERS dual sensor to determine CPF was developed.•MIPs were synthesized by bulk polymerization to extract CPF from apple juice.•CPF in apple juice at concentrations ...≥5mgL−1 was detected by naked eyes.•UV and Raman spectroscopies quantified CPF in apple juice at 0.1 and 0.01mgL−1.•Rapid determination of trace level of CPF in apple juice was achieved (<25min).
Chlorpyrifos (CPF), an organophosphate insecticide, is widely identified in fruit juices. In this study, a novel molecularly imprinted polymers-surface-enhanced Raman spectroscopy (MIPs-SERS)/colorimetric dual sensor was developed to determinate CPF in apple juice. MIPs were synthesized using bulk polymerization to rapidly and selectively adsorb and separate CPF from apple juice. A colorimetric method was developed based upon color changes of synthesized silver nanoparticles (AgNPs) by interacting with CPF, while SERS spectra were directly collected by illuminating the aggregated AgNPs with Raman laser. Colorimetric method rapidly screened and semi-quantified CPF in apple juice ≥5mgL−1 by naked eye, or accurately quantified CPF in apple juice ranging 0.1–10mgL−1 by UV–vis spectroscopy. Principle component analysis and partial least-squares regression models (RMSEC=0.0453, R2-C=0.9885) validated using SERS to further quantify CPF in apple juice at extremely low concentration (0.01mgL−1). This MIPs-SERS/colorimetric dual sensor can rapidly (<25min), accurately, and cost-efficiently determine CPF in apple juice and meet the worldwide regulation of maximum residue limit.
For polymer particles, recent studies emphasized that the particle shape—not size—plays the dominant role in novel applications in fields ranging from nanotechnology, biomedicine, to photonics, which ...has intensified the quest for fabrication platforms of polymer colloids with complex non-spherical (anisotropic) shapes. Here, we developed a single-step, microfluidic-supported synthesis for anisotropic polyvinyl methacrylate (PVMA) nanoparticles (NPs) by combining the advantages of microfluidics (providing homogeneous conditions for the initial emulsification process) and bulk batch synthesis (providing inhomogenous conditions for the thermal polymerization). Specifically, we tested five interfacial agents regarding their direct impact on the NP shape (from isotropic spherical to anisotropic flower-like shapes) and their concentration-dependent impact (from 0.1 mM to 20 mM) on the NP diameter (from 200 nm to 50 nm). We employed vinyl methacrylate (VMA), a monomer offering two-polymerization active sites. With our work, we contribute to a fundamental understanding of colloidal polymerization towards predictive shapes below the critical 200 nm regime.
Cyclic poly(
l
-lactide)s were prepared by ring-opening polymerization combined with simultaneous polycondensation (ROPPOC) in bulk at 160 °C with dibutyltin bis(4-cyanophenoxide) as catalyst. It is ...demonstrated by MALDI TOF mass spectrometry and
1
H NMR end group analyses that cycles are formed by end-to-end cyclization in addition to "back-biting" transesterification. Formation of high molar mass cyclic poly(
l
-lactide)s by means of several more reactive ROPPOC catalysts presented previously and in new experiments is discussed. These experimental results, together with theoretical arguments, prove that part of the Jacobson-Stockmayer theory is wrong. The critical monomer concentration, above which end-to-end cyclization is seemingly impossible, does not exist and reversible like irreversible polycondensations can theoretically proceed up to 100% conversion, so that finally all reaction products will necessarily adopt a cyclic architecture.
The results of this study show that even at the highest initial monomer concentration (IMC) complete cyclization of polymer chains can be achieved at 100% conversion.
Batch, in situ seeded and stepwise dosing monomer, and normal seeded soap‐free emulsion polymerizations (SFEP) of styrene were carried out by using the oil‐soluble 2,2′‐azobis(isobutyronitrile) as ...initiator. Gel permeation chromatography (GPC) and scanning electron microscopy were employed to characterize the experimental results. Typical auto‐accelerative effect in the bulk free‐radical polymerization was also observed in the macro‐kinetics of batch SFEP at 60 and 65°C. Flat‐roof GPC curves appeared at the post‐auto‐acceleration. In addition, Mn¯ in particles exhibited a positive relationship with the size of particles. The bigger size the larger Mn¯. In the in situ seeded polymerization, the flat‐roof GPC curves of seed turned into the asymmetric Gaussian type exhibiting the great increase of the fraction of larger Mn¯ with the sequential addition of styrene. In addition, the number of seeds was kept constant throughout the polymerization. It indicated that the free radicals were generated and confined in the growing particles. In the normal seeded polymerization, Mn¯ showed a strong dependence on the average assigned amount of St per seed particle. The more monomers per seed particle the larger Mn¯ was gained. Based on these results, it was postulated that the free radicals were living due to the gel effect occurring in particles, namely that the free radicals were segregated by the dry polymer chains. The kinetics model was also given based on the microdroplets theory.
Results of in situ seeded and stepwise dosing monomer experiments imply the living free‐radicals in particles due to gel effect.
Lightweight and nanoporous composite materials with excellent thermal insulation and strong mechanical property are urgently required to address prominent issues that pertain to application. The main ...challenge of synthesizing such materials is to reduce the thermal conductivity and improve its rigid-flexible combined property as well as its heat resistance. Here, we propose to prepare a completely lightweight 3D bulk composites by vacuum impregnation and gel polymerization processing with a needled quartz fiber felt (NQF) as the reinforcement and phenolic resin aerogel (PR) as the matrix. The nanoporous PR is facilely synthesized by polymerization-induced phase separation with phenolic resin, and the resultant nanoporous PR is uniformly filled and distributed in NQF without macroscopic cracking and agglomeration. The as-prepared NQF/PR nanocomposites possessed enhanced mechanical property with compressive strength (1.76–2.84 MPa) and Young's modulus (26.71–39.60 MPa) in the xy direction. Importantly, the NQF/PR nanocomposite was not damaged as the strain reached 50% in z direction. Compared to most organic-based aerogel and aerogel-like materials, the present NQF/PR nanocomposite aerogels exhibited excellent flame resistances with 1000 °C fire duration time exceeding 30 min and excellent thermal insulation properties with low thermal conductivities that varied from 0.017 W/m⋅K to 0.031 W/m⋅K. This experimental results show that the synthesized NQF/PR nanocomposites by this method are very suitable to heat high-performance lightweight insulation materials for industrial compatibly and production.
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The development of plastic scintillators loaded with low-cost phosphorescent sensitizer is currently an important topic toward enhancing the scintillation light yield for radiation detection ...applications. In this work, we report plastic scintillators loaded with deep-blue-emitting phosphorescent sensitizer CuI(PPh3)2(t-BuPy), where PPh3 and t-BuPy stand for triphenylphosphine and 4-tert-butylpyridine, respectively. CuI(PPh3)2(t-BuPy)-loaded poly(vinyltoluene)-based plastic scintillators with high optical transmittance of over 80% were synthesized via bulk polymerization method. The optical absorption, photoluminescence spectra, decay kinetics, and scintillation performance under X-ray, γ-ray, and α-particle excitation were comprehensively investigated. The scintillation yield was reduced with the increase of CuI(PPh3)2(t-BuPy) loading concentration. The physical mechanism and the role of the copper iodide complex in scintillation yield reduction are proposed.
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•Poly(vinyltoluene)-based plastic scintillators loaded with phosphorescent sensitizer CuI(PPh3)2(t-BuPy) were synthesized.•The scintillation yield of PVT scintillators is reduced with the increase of CuI(PPh3)2(t-BuPy) loading concentration.•The scintillation yield reduction is associated with the nonradiative dissipation of energy from CuI(PPh3)2(t-BuPy).•Plastic scintillator containing only CuI(PPh3)2(t-BuPy) showed α/γ PSD performance.
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