Addition-fragmentation Chain Transfer Precipitation Polymerization Research Articles

One-Pot Preparation of Ratiometric Fluorescent Molecularly Imprinted Polymer Nanosensor for Sensitive and Selective Detection of 2,4-Dichlorophenoxyacetic Acid

The development of fluorescent molecular imprinting sensors for direct, rapid, and sensitive detection of small organic molecules in aqueous systems has always presented a significant challenge in the field of detection. In this study, we successfully prepared a hydrophilic colloidal molecular imprinted polymer (MIP) with 2,4-dichlorophenoxyacetic acid (2,4-D) using a one-pot approach that incorporated polyglycerol methacrylate (PGMMA-TTC), a hydrophilic macromolecular chain transfer agent, to mediate reversible addition-fragmentation chain transfer precipitation polymerization (RAFTPP). To simplify the polymerization process while achieving ratiometric fluorescence detection, red fluorescent CdTe quantum dots (QDs) and green fluorescent nitrobenzodiazole (NBD) were introduced as fluorophores (with NBD serving as an enhancer to the template and QDs being inert). This strategy effectively eliminated background noise and significantly improved detection accuracy. Uniform-sized MIP microspheres with high surface hydrophilicity and incorporated ratiometric fluorescent labels were successfully synthesized. In aqueous systems, the hydrophilic ratio fluorescent MIP exhibited a linear response range from 0 to 25 μM for the template molecule 2,4-D with a detection limit of 0.13 μM. These results demonstrate that the ratiometric fluorescent MIP possesses excellent recognition characteristics and selectivity towards 2,4-D, thus, making it suitable for selective detection of trace amounts of pesticide 2,4-D in aqueous systems.

Synthesis of heat-resistant living polymer particles by one-step reversible addition-fragmentation chain transfer precipitation polymerization of styrene and N-phenylmaleimide

For the first time, the synthesis of heat-resistant, “living” polymer particles via one-step reversible addition-fragmentation chain transfer precipitation polymerization (RAFTPP) of styrene (St) and N-phenylmaleimide (PhMI) is reported. Gel permeation chromatography and nuclear magnetic resonance spectroscopy confirmed that the polymerization proceeded in a living manner. The scanning electron microscopy results showed that the monodisperse P(St-PhMI)_RAFTPP particles with a diameter of 1.88 μm were successfully synthesized. The P(St-PhMI)_RAFTPP showed excellent thermal stability with a high glass transition temperature and a 5% weight loss temperature. The surface concentration of the RAFT groups was determined to be 0.181 groups/nm2 due to fragmentation of the RAFT groups exposed on the particles. The small-angle neutron scattering measurements showed the particle formation mechanism, in which the swollen, growing polymer chains were consumed for particle formation. The introduction of grafted chains by surface-initiated RAFT polymerization demonstrated the possibility of further functionalization of P(St-PhMI)_RAFTPP particles by exploiting their living nature.

Capturing Cadmium(II) Ion from Wastewater Containing Solid Particles and Floccules Using Ion-Imprinted Polymers with Broom Effect

Cavities and adsorption sites in adsorption materials can be easily blocked in complex media containing solid particles and floccules, which limit the applicability of these materials. This study demonstrates the synthesis of cadmium(II) ion-imprinted polymers (Cd-IIPs) and nonion-imprinted polymers (NIPs) via reversible addition–fragmentation chain transfer precipitation polymerization (RAFTPP). Microspheres of IIPs and NIPs were modified by grafting bicomponent polymer brushes with different ratios of a hydrophilic component, hydroxyethyl methacrylate (HEMA), and a rigid component, styrene. The maximum adsorption capacities of the IIPs and NIPs in pure water are 65.5 and 24.5 mg/g, respectively. Specifically, the 9:1-IIP exhibits excellent antiblockage and anti-interference performance, with an adsorption capacity considerably higher than those of IIPs in simulated wastewater including SiO2 solid particles and floccules. This higher performance suggests that the 9:1-IIP has the rigidity to resist chaff ...

Preparation of hydrophilic surface-imprinted ionic liquid polymer on multi-walled carbon nanotubes for the sensitive electrochemical determination of imidacloprid

A hydrophilic ionic liquid monomer was immobilized on carboxylated MWNTs by ion exchange, then reversible addition–fragmentation chain transfer precipitation polymerization was performed in the presence of a template, imidacloprid.

Water-compatible temperature and magnetic dual-responsive molecularly imprinted polymers for recognition and extraction of bisphenol A

Versatile molecularly imprinted polymers (MIPs) have been widely applied to various sample matrices, however, molecular recognition in aqueous media is still difficult. Stimuli-responsive MIPs have received increasing attentions due to their unique feature that the molecular recognition is regulated by specific external stimuli. Herein, water-compatible temperature and magnetic dual-responsive MIPs (WC-TMMIPs) with hydrophilic brushes were prepared via reversible addition-fragmentation chain transfer precipitation polymerization for reversible and selective recognition and extraction of bisphenol A (BPA). Transmission electron microscopy (TEM), Fourier transform infrared spectrometer (FT-IR) and vibrating sample magnetometry (VSM) as characterization methods were used to examine the successful synthesis of polymers, and the resultant WC-TMMIPs showed excellent thermosensitivity and simple rapid magnetic separation. Controlled adsorption and release of BPA by temperature regulation were investigated systematically, and the maximum adsorption and removal efficiency toward BPA in aqueous solutions were attained at 35°C and 45°C, respectively, as well as a good recoverability was exhibited with the precision less than 5% through five adsorption–desorption cycles. Phenolic structural analogs were tested and good recognition specificity for BPA was displayed. Accordingly, the WC-TMMIPs were employed as adsorbents for magnetic solid-phase extraction (MSPE) and packed SPE of BPA from seawater samples. Using the two modes followed by HPLC-UV determination, excellent linearity was attained in the range of 0.1–14.5μM and 1.3–125nM, with low detection limits of 0.02μM and 0.18nM, respectively. Satisfactory recoveries for spiked seawater samples were achieved ranging from 86.3–103.5% and 96.2–104.3% with RSD within 2.12–4.33%. The intelligent WC-TMMIPs combining water-compatibility, molecular recognition, magnetic separation, and temperature regulation proved potentially applicable for selective identification, controlled adsorption/release and high-efficiency enrichment/removal of trace targets in complicated aqueous media.

Preparation and evaluation of vanillin molecularly imprinted polymer microspheres by reversible addition–fragmentation chain transfer precipitation polymerization

Novel vanillin molecularly imprinted polymer microspheres were synthesized by the method of the reversible addition–fragmentation chain transfer (RAFT) precipitation polymerization. In the study, the imprinted polymer was synthesized by using dibenzyltrithiocarbonate (DBTTC) and vanillin as the chain transfer agent and template respectively. Ultraviolet spectrum analysis was used to determine methacrylic acid (MAA) as the functional monomer. The conditions which influence the preparation of the molecularly imprinted polymer prepared by RAFT (RAFT-MIP) such as solvent, crosslinker, and the ratio of monomer, AIBN and DBTTC were systematically investigated. Scanning election microscopy, adsorption experiment and Scatchard analysis were used to evaluate the RAFT-MIP. The morphology and adsorption performance of RAFT-MIP were improved significantly in comparison with molecularly imprinted polymers synthesized by traditional precipitation polymerization (TR-MIP).

Water-compatible poly (hydroxyethyl methacrylate) polymer sorbent for miniaturized syringe assisted extraction of sulfonamides in milk

A simple, convenient, and economic self-assembly miniaturized syringe assisted extraction (mini-SAE) using poly (hydroxyethyl methacrylate) polymer (PHEMA) as sorbent coupled with liquid chromatography was proposed for rapid screening of sulfadiazine (SD) and sulfamonomethoxine (SMM) in milk. The water-compatible PHEMA was synthesized by reversible addition-fragmentation chain transfer precipitation polymerization using trithiocarbonate as chain transfer agent and methanol–water system as reaction medium. The obtained PHEMA sorbent showed good affinity to sulfonamides and was successfully applied as a special sorbent for a mini-SAE device for simultaneous extraction and isolation of SD and SMM in milk samples. Under the optimum condition, good linearity was obtained in a range of 7.0–700ngg−1 (r≥0.9995) and the average recoveries of SD and SMM at three spiked levels were ranged from 85.6 to 100.3% with the relative standard deviations (RSD) ≤6.5%. The presented PHEMA-mini-SAE protocol could be potentially applied as an alternative tool for analyzing the residues of SAs in complicated biological samples.

Molecularly imprinted polymers by reversible addition–fragmentation chain transfer precipitation polymerization for preconcentration of atrazine in food matrices

Controlled/living free radical polymerization (CLRP) has been accepted as an effective technique in preparation of polymers because of its inherent advantages over traditional free radical polymerization. In this work, reversible addition–fragmentation chain transfer (RAFT) polymerization, the ideal candidate for CLRP, was applied to prepare atrazine molecularly imprinted polymers (MIPs) by precipitation polymerization. The resultant RAFT-MIPs demonstrated uniform spherical shape with rough surface containing significant amounts of micropores, leading to an improvement in imprinting efficiency compared with that of the MIPs prepared by traditional precipitation polymerization (TR-MIPs). The maximum binding capacities of the RAFT-MIPs and TR-MIPs were 2.89mgg−1 and 1.53mgg−1, respectively. The recoveries ranging from 81.5% to 100.9% were achieved by one-step extraction by using RAFT-MIPs for preconcentration and selective separation of atrazine in spiked lettuce and corn samples. These results provided the possibility for the separation and enrichment of atrazine from complicated matrices by RAFT-MIPs.

Preparation of molecularly imprinted polymer microspheres via reversible addition–fragmentation chain transfer precipitation polymerization

The first combined use of reversible addition–fragmentation chain transfer (RAFT) polymerization and precipitation polymerization in the molecular imprinting field is described. The new polymerization technique, namely RAFT precipitation polymerization (RAFTPP), provides MIP microspheres with obvious molecular imprinting effects towards the template, fast template binding process and an appreciable selectivity over structurally related compounds, while only irregular MIP aggregates were obtained via traditional radical precipitation polymerization (TRPP) under similar reaction conditions. The MIP microspheres prepared via RAFTPP have proven to show improved binding capacity, larger binding constant and apparent maximum number for high-affinity sites, and significantly higher high-affinity binding site density in comparison with the MIP prepared via TRPP.