Bulk Polymerization Research Articles

Cross-linking of triblock copolymers of functionalized poly(caprolactone) and poly(ethylene glycol): The effect on the formation of viscoelastic thermogels

The objective of this study was to develop methods for reproducible production of partially cross-linked copolymers based on poly(α-benzyl carboxylate-ε-caprolactone) and poly(ethylene glycol) (abbreviated as PBCL-PEG-PBCL) and assess the effect of the type and/or molar ratio of cross-linker to polymer on the formation of viscoelastic thermogels. For this purpose, PBCL-PEG-PBCL block copolymers were prepared through ring-opening polymerization of α-benzyl-ε-caprolactone (BCL) and PEG (1450 kDa) through bulk polymerization. This was followed by the addition of either polycaprolactone triol (PCL-triol), trimethylolpropane (TMP) ethoxylate, or PEG (200 or 400 Da), as potential chemical cross-linkers. Formation of a high molecular weight polymer population for copolymer prepared in the presence of all cross-linkers under study was evidenced through comparison of data from 1H NMR spectroscopy and gel permeation chromatography (GPC). Among different polyols, only the copolymers partially cross-linked with PEG 400 at PEG 400/BCL ratio of 4:10 formed thermo-reversible viscoelastic hydrogels with sol-gel transition temperatures around 23 °C at a concentration of 15% (w/w). The results implied favoured physical association of PEG400 cross-linked or branched PBCL-PEG-PBCL micelles to contribute to the thermo-responsive gelation and viscoelastic behaviour of the product.

Ultrathin and Super Strong UHMWPE Supported Composite Anion Exchange Membranes with Outstanding Fuel Cells Performance.

For high-performance anion exchange membrane fuel cells (AEMFCs), the anion exchange membrane (AEMs) should be as thin as possible to reduce the ohmic resistance. However, the mechanical stability of ultrathin AEMs cannot be guaranteed, as well as a huge risk of gas (H2 &O2 ) permeation. In this work, composite AEMs based on ultrahigh molecular weight polyethylene (UHMWPE) are prepared by in situ bulk polymerization. The as-prepared composite membranes can be as thin as 4µm, and possess super high strength beyond 150MPa. It also shows extremely low hydrogen permeation, low water uptake, low dimensional swelling, high conductivity, and good alkaline stability. In addition, the fuel cell performance based on the ultrathin composite AEMs exhibits outstanding peak power density of 1014 and 534mW cm-2 for H2 -O2 and H2 -Air (CO2 -free) at 65°C, respectively, as well as good short-term durability.

Solventless solid‐phase extraction using Zn ion‐imprinted polymer detected by colorimetric method

AbstractIon‐imprinted polymers attract a lot of attention and are actively studied because of easy preparation and their high selectivity. Zn is known to be essential mineral in human body; however, when it is absorbed into our body, it is hardly discharged completely and causes various disease or side effects. To suggest new method for selective Zn extraction, Zn ion‐imprinted polymer (ZIIP) was synthesized by bulk polymerization and NZIIP (non‐ZIIP) was prepared as a control. Then, ZIIP and NZIIP were characterized by Fourier‐transform infrared spectroscopy, Scanning electron microscope, and X‐ray photoelectron spectroscopy to investigate structural changes during polymerization. Adsorption isotherm studies indicated that sigmoidal Langmuir isotherm equation was fitted well and the maximum adsorption capacity and affinity of Zn on ZIIP was superior to NZIIP. Dithizone was used to chelate with Zn in supernatant for colorimetric determination. ZIIP‐solid‐phase extraction potentially used as Zn ion filter was investigated showing good removal efficiency.

Synthesis of poly(vinyl alcohol) by blue light bismuth oxide photocatalysed RAFT. Evaluation of the impact of freeze/thaw cycling on ice recrystallisation inhibition.

Poly(vinyl alcohol), PVA, is the most potent polymeric ice recrystallisation inhibitor (IRI), mimicking a complex function of ice binding proteins. The IRI activity of PVA scales with its molecular weight and hence broad molecular weight distributions in free radical-derived PVAs lead to activity measurements dominated by small amounts of heavier fractions. Well-defined PVA can be prepared by thermally initiated RAFT/MADIX polymerization using xanthates by the polymerization of the less activated monomer vinyl acetate. The low conversions and molecular weights obtained during this approach, often requires feeding of additional initiator and bulk polymerization. Here we employ bismuth oxide photo-RAFT in solution, using blue light (450 nm), rather than previously reported white light, to obtain a library of PVA's. The use of blue light enabled quantitative conversion and acceptable dispersities. Purple light (380 nm) was also used, but asymmetric molecular weight distributions were obtained in some cases. High concentrations of high molecular weight PVA is known to form cryogels during freeze/thaw which has led to speculation this might limit the use of PVA in environments where the temperature cycles e.g. the construction industry. After 4 freeze/thaw cycles there was only small changes in observable IRI for all synthesised PVAs and two commercial standards. In an extended test, activity was retained after 100 freeze/thaw cycles, mitigating concerns that PVA could not be used in situations where freeze/thaw cycles occur. This work presents a convenient method to obtain well-defined PVAs for cryoscience studies compared to conventional thermal-RAFT and indicates that cryogelation concerns may not prevent their use.

Significantly improving mechanical properties of epoxy resin-based carbon fiber-reinforced plastic composites via introducing oxazolidinone segments

Herein, the oxazolidinone (OX) segments have been successfully introduced into carbon fiber-reinforced plastic (CFRP) composites via the bulk polymerization of the isocyanate and epoxy (EP) groups to significantly promote the mechanical properties. Through the bulk polymerization, the OX segments in epoxy resin (OX epoxy resin) have been formed, verified via the Fourier transform infrared (FT-IR) spectroscopy. Afterward, in order to obtain the cured OX epoxies, the as-prepared OX epoxy resin has been mixed with the pure EP resin for further curing. Thermogravimetric analysis (TGA) and dynamic mechanical thermal analysis (DMTA) have shown that the cured OX epoxies have exhibited improved thermal resistance and higher Tg than the cured neat epoxies. After introducing OX segments, the flexural strength, flexural modulus, and impact strength of the cured OX epoxies have been promoted by 30.1%, 12.1%, and 82.9%, respectively. Moreover, the mechanical properties of CFRP composites, fabricated from OX epoxy resin and T1100 carbon fibers, have been improved as well and in particular, the flexural strength, flexural modulus, impact strength, interlaminar shear strength, and compressive strength after the impact of the composites have been improved by 25.9%, 8.4%, 23.6%, 35.5%, and 23.8%, respectively. Furthermore, the impact damage of the composite laminates has been analyzed via Ultrasonic C-scan.

Sulfur-rich polymer nanoparticles prepared by miniemulsion polymerization.

The inclusion of sulfur in polymer materials is becoming an excellent strategy to exploit the large feedstock of elemental sulfur produced as waste by the oil industry. However, the resulting polymers have limited processability. Here we leverage the benefits of polymerization in dispersed media to produce suspensions of sulfur-rich polymer latexes that are water processable.

Segmented shape memory polyurethane: Influence of soft segment types and length

Shape-memory polyurethanes (SMPUs) with heat induced characteristic can be altered to a programmed shape and return to its original shape upon thermal stimuli. SMPU has prompted a lot of interest for various applications such as biomedical appliances, fabrics, coatings, and sensors. In this study, a series of polyols (polycaprolactone (PCL), polyethylene glycol (PEG), polypropylene glycol (PPG)) with different molecular weight were used to synthesize SMPU together with 4,4-methylenebis(cyclohexyl isocyanate) (HMDI) as diisocyanate, and 1,4-butanediol (BD) as chain-extender via two-step bulk polymerization technique. Palm kernel oil-based polyol (PKO-p) was introduced as part of the soft segment. The SMPUs were analyzed using Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), differential scanning calorimetry (DSC), shape memory and tensile tests. The results showed that SMPU with lower molecular weight (PU-PCL2) achieved higher tensile strength (7.58 MPa) compared to higher molecular weight of PCL (1.55 MPa) apparently due to the low crystallinity. Moreover, PEG based SMPU (PU-PEG3) exhibited good shape memory property with 82% of shape fixity and shape recovery of more than 80%. It was revealed that the variation in molecular weight of the soft segments provides significant effects on the tensile and shape memory properties of SMPU.

A Novel Ion-Imprinted Polymer Based on Principle of Ion Exchange by Bulk Polymerization for Specific Recognition and Adsorption of Nitrate in Polluted Groundwater

A Novel Ion-Imprinted Polymer Based on Principle of Ion Exchange by Bulk Polymerization for Specific Recognition and Adsorption of Nitrate in Polluted Groundwater

Fabrication and mechanical properties of knitted dissimilar polymeric materials with movable cross-links

Movable cross-network elastomer with knitting polymers (KP elastomer) were obtained by bulk polymerization of main chain monomers in presence of host polymer. The two design strategies successfully improve the toughness and stiffness of the KP elastomers.

Merging photoinitiated bulk polymerization and the dopant-matrix design strategy for polymer-based organic afterglow materials

The polymer produced by photoinitiated bulk polymerization promotes intersystem crossing of luminescent dopants and switches on room-temperature organic afterglow.

High strength, epoxy cross-linked high sulfur content polymers from one-step reactive compatibilization inverse vulcanization.

Inverse vulcanization provides a simple, solvent-free method for the preparation of high sulfur content polymers using elemental sulfur, a byproduct of refining processes, as feedstock. Despite the successful demonstration of sulfur polymers from inverse vulcanization in optical, electrochemical, and self-healing applications, the mechanical properties of these materials have remained limited. We herein report a one-step inverse vulcanization using allyl glycidyl ether, a heterobifunctional comonomer. The copolymerization, which proceeds via reactive compatibilization, gives an epoxy cross-linked sulfur polymer in a single step, as demonstrated through isothermal kinetic experiments and solid-state 13C NMR spectroscopy. The resulting high sulfur content (≥50 wt%) polymers exhibited tensile strength at break in the range of 10–60 MPa (70–50 wt% sulfur), which represents an unprecedentedly high strength for high sulfur content polymers from vulcanization. The resulting high sulfur content copolymer also exhibited extraordinary shape memory behavior along with shape reprogrammability attributed to facile polysulfide bond rearrangement.

Chain-length dependence of the propagation rate coefficient for methyl acrylate polymerization at 25 °C investigated by the PLP-SEC method

The marked chain-length dependence of the propagation rate coefficient of long-chain radicals has been determined for methyl acrylate bulk polymerization at 25 °C through the analysis of data obtained by the PLP-SEC method applying novel approaches.

Purification and Clean-up of 3-NPA from Sugarcane by using Molecularly Imprinted Polymer Solid Phase Extraction Coupled with HPLC-siftdesk

The agricultural product is in constant need of improved analytical techniques that can be used to control the manufacturing process and the food safety of the products. A new selective material based on molecularly imprinted polymers (MIPs) were prepared by bulk polymerization methods and used as solid-phase extraction (SPE) sorbent for sample enhancement of 3-nitropropanic acid (3-NPA) in sugarcane samples prior to high-performance liquid chromatography (HPLC). The objective of this work was to devolved techniques for the extraction, purification, clean up, and preconcentration of 3-NPA from sugarcane samples employing MIP for SPE. The obtained polymers were characterized using field emission scanning electron microscopy, Fourier transforms infrared and the adsorption capacity of SA-SMIP was studied. The developed MISPE method showed excellent linearity in the range of 40–70 mg L with coefficient of determination (r²) >0.9997 and good 3-NPA recoveries of >99% and limits of detection LOD and LOG were ranging from 0.19 mg L to 0.58 mg L, respectively. The method was successfully applied to the analysis of 3-NPA in selected sugarcane samples. MIP-SPE allows not only the analyte to be pre-concentrated but also removed the other compounds from the sample matrix. The MISPE technique has been successfully applied to purification, preconcentration, and clean-up of 3-nitropropionic acid in poisoning sugarcane.

Ion imprinted-carbon paste electrode as electrochemical sensor for ultra-trace recognizing speciation of mercury

Monitoring and determination of mercury species in the environment is a challenging issue. This work presents an electrochemical sensor based on voltammetric methods for selective recognition of Hg species using carbon paste electrode modified Hg2+-imprinted polymers. The ion-imprinted polymers were prepared by thermal bulk polymerization with Hg(NO3)2, 1,5-dipenylcarbazone (DPC), and ethylene glycol dimethacrylate (EGDMA) as template, ligand, and monomer, respectively. The surface properties of the electrode were characterized by scanning electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy, fourier transform infrared spectroscopy, thermal gravimetric analysis, electrochemical impedance spectroscopy, and cyclic voltammetry. In addition, differential pulse voltammetry was used to evaluate the electrochemical properties of the proposed sensors. The designed sensor was shown a wide linear range between 0.1 and 40 μM with a limit of detection (LOD) at 70 nM (3σ). The sample analysis found that the sensor has good stability and selectivity for mercury speciation with a %recovery of 98–103 %.

Influence of prepolymer reaction time in the fabrication of palm kernel oil polyol based shape memory polyurethane

AbstractVegetable oil‐based shape memory polyurethane (SMPU) has been rapidly developed in the field of advanced polymeric materials due to its unique responsive characteristic. This research aimed to investigate the effect of prepolymer reaction time on the microphase separation, soft segment crystallinity, shape memory, and tensile properties of palm kernel oil polyol (PKO‐p)‐based SMPU. The SMPU samples were prepared via two‐step bulk polymerization process utilizing 4,4‐methylenebis (cyclohexyl isocyanate) (HMDI), polycaprolactone diol (PCL) and 1,4‐butanediol (BD). The reaction time after the addition of PKO‐p varied from 0.5 to 2.5 h in prepolymer synthesis. This reaction time resulted in excellent microphase separation and improve shape memory properties. The Fourier transform infra‐red analysis revealed that the degree of microphase separation of the polyurethane elastomer (PUE) increased with increasing prepolymer reaction time. In consequence, the shape fixity behavior of the PUE samples improved. The tensile strength and strain at break of PUE increased with increasing reaction time up to 2.0 h. However, when the reaction time was prolonged to 2.5 h, both values decreased. Thus, the results showed the advantages of using PKO‐p, which can minimize the usage of petroleum‐based polyol and improve the tensile and shape memory behavior of the PKO‐p‐based SMPU.

Micropatterning of acoustic droplet vaporization in acoustically-responsive scaffolds using extrusion-based bioprinting

Acoustically-responsive scaffolds (ARSs) are composite hydrogels that respond to ultrasound in an on-demand, spatiotemporally-controlled manner due to the presence of a phase-shift emulsion. When exposed to ultrasound, a gas bubble is formed within each emulsion droplet via a mechanism termed acoustic droplet vaporization (ADV). In previous in vitro and in vivo studies, we demonstrated that ADV can control regenerative processes by releasing growth factors and/or modulating micromechanics in ARSs. Precise, spatial patterning of emulsion within an ARS could be beneficial for ADV-induced modulation of biochemical and biophysical cues. However, precise patterning is limited using conventional bulk polymerization techniques. Here, we developed an extrusion-based method for bioprinting ARSs with micropatterned structures. Emulsions were loaded within bioink formulations containing fibrin, hyaluronic acid and/or alginate. Experimental as well as theoretical studies elucidated the interrelations between printing parameters, needle geometry, rheological properties of the bioink, and the process-induced mechanical stresses during bioprinting. The shear thinning properties of the bioinks enabled use of lower extrusion pressures resulting in decreased shear stresses and shorter residence times, thereby facilitating high viability for cell-loaded bioinks. Bioprinting yielded greater alignment of fibrin fibers in ARSs compared to conventionally polymerized ARSs. Bioprinted ARSs also enabled generation of ADV at high spatial resolutions, which were otherwise not achievable in conventional ARSs, and acoustically-driven collapse of ADV-induced bubbles. Overall, bioprinting could aid in optimizing ARSs for therapeutic applications.

SERS paper slip based on 3D dendritic gold nanomaterials coupling with urchin-like nanoparticles for rapid detection of thiram

A paper-based surface-enhanced Raman scattering (SERS) sensor that combined the excellent performance of three-dimensional (3D) dendritic gold (DAu) matrix and the selective adsorption ability of biomimetic recognition polymer (BRP) has been constructed for ultrasensitive detection of thiram. The 3D DAu structure decorated on cellulosic matrix provides predominant SERS performance and chemical stability for the analytical platform. Compared with two-dimensional (2D) SERS platforms, it can get efficient utilization of 3D laser excitation volume to achieve optimal SERS enhancement. BRP membranes for the specific recognition and enrichment of thiram were prepared by bulk polymerization. And the urchin-like nanoparticles (UNPs) with rich cutting-edge structure were decorated in the BRP to provide sufficient “hot spots”. In the region where DAU was close to UNPS, the synergistic SERS enhancement was generated through particle plasmon coupling. And the whole structure of the composite multilayer provides multiple SERS enhancement for thiram detection. The SERS response of the sensor toward thiram showed excellent correlation during the range of 1 × 10−10 to 1 × 10−7 mol·L−1 with the detection limits as low as 2.75 × 10−11 mol·L−1. The test results of selectivity, reproducibility, and accuracy indicated that the paper-based DAu/BRP (UNPs) sensor possessed potential applications in pesticides analytical and other related fields.

Kinetic Modeling of Ring Opening Polymerization of Lactones under Microwave Irradiation

AbstractA kinetic study on the mathematical modeling of polymerization rate and molar mass development in the ring opening bulk polymerization (ROP) of lactones under microwave irradiation (MI), for the production of biodegradable green polymers used in the biomedical sector, is presented. Two modeling approaches, one based on calculation of average properties using a self‐developed code based on the method of moments, and the other one providing calculation of full molar mass distributions with the aid of the Predici software are contrasted. The observed enhancement on polymerization rate under MI is captured well by using a non‐thermal microwave effect modeling approach, namely, a microwave‐enhanced propagation model. The proposed approach is validated with available experimental data for ROP of ε‐caprolactone, a monomer which can be obtained from biomasses, using benzyl alcohol (BzOH) and stannous octoate (SnOc)2 as initiator and catalyst, respectively, at 150 °C. Seven case studies are analyzed, including ROPs carried out under both conventional heating (CH) and MI. The effect of initiator and alcohol initial concentrations on polymerization rate and molar mass distributions is analyzed. The advantages of using MI in ROP are assessed.

Bilobalide molecularly imprinted polymers prepared using MWCNTs/ZIF‐67 composite as supporter for solid‐phase extraction of bilobalide from real samples

AbstractThe preparation of raw materials is an important prerequisite for studying the function of natural active ingredients. Here, the preparation of MWCNTs/ZIF‐67@MIPs based on surface molecular imprinting technology for the separation of bilobalide (BB) from real samples was proposed. The successful preparation of MWCNTs/ZIF‐67@MIPs was demonstrated using several techniques. Adsorption equilibrium was achieved when the time was 4 h, and the rate of adsorption calculated from the dynamic adsorption results was 14.2 μg mL–1 h–1. The maximum adsorption amount for MWCNTs/ZIF‐67@MIPs of BB was calculated to be 59.2 mg g–1, which was more than three times that for MWCNTs/ZIF‐67@NIPs (23.1 mg g–1), and the Freundlich isotherm model and pseudo‐second‐order kinetic model were more suitable for the explanation of isothermal and kinetic adsorption behaviors, respectively. The results of selective adsorption indicated that MWCNTs/ZIF‐67@MIPs show excellent selectivity and specificity for BB compared to structurally similar compounds such as ginkgolides A, B and C, with an excellent imprinting factor (2.83). The results of reuse studies indicated that MWCNTs/ZIF‐67@MIPs exhibited great reproducibility with a recovery rate of 70.8% after repeated use for five times. Finally, the developed MWCNTs/ZIF‐67@MIPs were used as a solid‐phase extraction sorbent to directly separate BB from treated gingko leaf extract and crude extract of BB, and the results suggested that the purity of BB in the two samples was increased by about 30%, and the recoveries reached 68.34% and 71.54%, respectively. Meanwhile, the separation effect of MWCNTs/ZIF‐67@MIPs on BB was better than that of BBMIP prepared by bulk polymerization. © 2021 Society of Industrial Chemistry.

The Influence of Silica Nanoparticles on the Thermal and Mechanical Properties of Crosslinked Hybrid Composites.

This paper presents the synthesis and physicochemical characterization of a new hybrid composite. Its main goals are evaluating the structure and studying the thermal and mechanical properties of the crosslinked polymeric materials based on varying chemical properties of the compounds. As an organic crosslinking monomer, bisphenol A glycerolate diacrylate (BPA.GDA) was used. Trimethoxyvinylsilane (TMVS) and N-vinyl-2-pyrrolidone (NVP) were used as comonomers and active diluents. The inorganic fraction was the silica in the form of nanoparticles (NANOSiO2). The hybrid composites were obtained by the bulk polymerization method using the UV initiator Irqacure 651 with a constant weight ratio of the tetrafunctional monomer BPA.GDA to TMVS or NVP (7:3 wt.%) and different wt.% of silica nanoparticles (0, 1, 3%). The proper course of polymerization was confirmed by the ATR/FTIR spectroscopy and SEM EDAX analysis. In the composites spectra the signals correspond to the C=O groups from NVP at 1672–1675 cm−1, and the vibrations of Si–O–C and Si–O–Si groups at 1053–1100 cm−1 from TMVS and NANOSiO2 are visible. Thermal stabilities of the obtained composites were studied by a differential scanning calorimetry DSC. Compared to NVP the samples with TMVS degraded in one stage (422.6–425.3 °C). The NVP-derived materials decomposed in three stages (three endothermic effects on the DSC curves). The addition of NANOSiO2 increases the temperature of composites maximum degradation insignificantly. Additionally, the Shore D hardness test was carried out with original metrological measurements of changes in diameter after indentation in relation to the type of material. The accuracy analysis of the obtained test results was based on a comparative analysis of graphical curves obtained from experimental tests. The values of the changes course of similarity in the examined factors, represented by those of characteristic coefficients were determined based on the Fréchet’s theory.