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A new and simple strategy towards electric-field-driven multiple chirality switching device has been designed and fabricated by combining a newly synthesized base-responsive chiroptical polymer switch (R-FLMA) and p-benzoquinone (p-BQ) via proton-coupled electron transfer (PCET) mechanism. Clear and stable triple chirality states (silence, positive, negative) of this device in visible band can be regulated reversibly (>1000 cycles) by adjusting voltage programs. Furthermore, such chiral switching phenomena are also accompanied by apparent changes of color and fluorescence. More importantly, the potential application of this device for a spatial light modulator has also been demonstrated.

The facile and efficient one-pot synthesis of monodisperse, highly crosslinked, and “living” functional copolymer microspheres by the ambient temperature iniferter-induced “living” radical precipitation polymerization (ILRPP) is described for the first time. The simple introduction of iniferter-induced “living” radical polymerization (ILRP) mechanism into precipitation polymerization system, together with the use of ethanol solvent, allows the direct generation of such uniform functional copolymer microspheres. The polymerization parameters (including monomer loading, iniferter concentration, molar ratio of crosslinker to monovinyl comonomer, and polymerization time and scale) showed much influence on the morphologies of the resulting copolymer microspheres, thus permitting the convenient tailoring of the particle sizes by easily tuning the reaction conditions. In particular, monodisperse poly(4-vinylpyridine-co-ethylene glycol dimethacrylate) microspheres were prepared by the ambient temperature ILRPP even at a high monomer loading of 18 vol %. The general applicability of the ambient temperature ILRPP was confirmed by the preparation of uniform copolymer microspheres with incorporated glycidyl methacrylate. Moreover, the “livingness” of the resulting polymer microspheres was verified by their direct grafting of hydrophilic polymer brushes via surface-initiated ILRP. Furthermore, a “grafting from” particle growth mechanism was proposed for ILRPP, which is considerably different from the “grafting to” particle growth mechanism in the traditional precipitation polymerization. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013

Molecular imprinting is a versatile and straightforward method for the preparation of polymer receptors with tailor-made recognition sites. Despite the tremendous progress made in this field, many challenges still remain to be addressed. In particular, it has been shown that the presently developed molecularly imprinted polymers (MIPs) are normally only organic solvent compatible and they mostly fail to show specific template bindings in pure aqueous solutions, thus significantly limiting their practical applications in the field of biotechnology. Although some approaches, which either use specifically designed functional monomers or apply the conventional imprinting protocol, have been developed for the preparation of MIPs with molecular recognition ability under aqueous conditions, versatile approaches for the preparation of MIPs that are applicable in pure aqueous environments are still rare. Herein, we report a new and efficient one-pot approach to obtain pure-water-compatible and narrowly dispersed MIP microspheres with surface-grafted hydrophilic polymer brushes by facile reversible addition/fragmentation chaintransfer (RAFT) precipitation polymerization (RAFTPP), mediated by hydrophilic macromolecular chain-transfer agents (Macro-CTAs; Scheme 1). The presence of hydrophilic polymer brushes on MIP microspheres significantly improved their surface hydrophilicity and dramatically reduced their hydrophobic interactions with template molecules in pure aqueous media, thus leading to their water compatibility. The easy availability of many different hydrophilic Macro-CTAs (by either RAFT polymerization of hydrophilic monomers or hydrophilic polymer end group modification), together with the versatility of RAFTPP for the controlled preparation of MIP microspheres, makes this strategy highly applicable for the design of hydrophilic and water-compatible MIPs. Two strategies have been developed for the synthesis of water-compatibleMIPs by improving their surface hydrophilicity; these strategies involve the use of a hydrophilic comonomer, functional monomer, or crosslinker in the molecular imprinting process, and the postmodification of the preformed MIPs. Although simple in principle, the former strategy either requires time-consuming optimization of MIP formulation components or can only be applied in some special systems. In comparison, the latter strategy, which involves the surface grafting of hydrophilic polymer layers, has proven highly attractive because it not only significantly improves the MIPs surface hydrophilicity, but also provides a protective layer to prevent protein molecules from blocking their imprinting sites in biological solutions. Very recently, we have successfully prepared pure-water-compatible MIP microspheres by the controlled grafting of hydrophilic polymer layers onto the preformed MIP particles. Compared with this two-step approach, the new strategy presented herein allows the more efficient controlled synthesis of pure-water-compatible MIP microspheres with surface-grafted hydrophilic polymer brushes by a one-pot RAFTPP method. To show proof-of-principle for our strategy, a model noncovalent molecular imprinting system was chosen because Scheme 1. Chemical structures of the utilized RAFT agents (including hydrophilic Macro-CTAs and CDB) and the schematic protocol for the one-pot preparation of water-compatible MIP microspheres by RAFT precipitation polymerization.

This article describes for the first time the development of a new polymerization technique by introducing iniferter-induced “living” radical polymerization mechanism into precipitation polymerization and its application in the molecular imprinting field. The resulting iniferter-induced “living” radical precipitation polymerization (ILRPP) has proven to be an effective approach for generating not only narrow disperse poly(ethylene glycol dimethacrylate) microspheres but also molecularly imprinted polymer (MIP) microspheres with obvious molecular imprinting effects towards the template (a herbicide 2,4-dichlorophenoxyacetic acid (2,4-D)), rather fast template rebinding kinetics, and appreciable selectivity over structurally related compounds. The binding association constant Ka and apparent maximum number Nmax for the high-affinity sites of the 2,4-D imprinted polymer were determined by Scatchard analysis and found to be 1.18 × 104 M−1 and 4.37 μmol/g, respectively. In addition, the general applicability of ILRPP in molecular imprinting was also confirmed by the successful preparation of MIP microspheres with another template (2-chloromandelic acid). In particular, the living nature of ILRPP makes it highly useful for the facile one-pot synthesis of functional polymer/MIP microspheres with surface-bound iniferter groups, which allows their direct controlled surface modification via surface-initiated iniferter polymerization and is thus of great potential in preparing advanced polymer/MIP materials. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3217–3228, 2010

The first application of atom transfer radical "bulk" polymerization (ATRBP) in molecular imprinting is described, which provides molecularly imprinted polymers (MIPs) with obvious imprinting effects towards the template, very fast binding kinetics, and an appreciable selectivity over structurally related compounds. In comparison with the MIP prepared via the normally used traditional "bulk" free radical polymerization (BFRP), the MIPs obtained via ATRBP showed somewhat lower binding capacities and apparent maximum numbers N max for high-affinity sites as well as quite similar binding association constants K a for high-affinity sites and high-affinity site densities, in contrast with the previous reports (e.g., nitroxide/ iniferter-mediated "bulk" polymerization provided MIPs with improved properties). This is tentatively ascribed to the occurrence of rather fast gelation process in ATRBP, which greatly restricted the mobility of the chemical species, leading to a heavily interrupted equilibrium between dormant species and active radicals and heterogeneous polymer networks. In addition, the general applicability of ATRBP was also confirmed by preparing MIPs for different templates. This work clearly demonstrates that applying controlled radical polymerizations (CRPs) in molecular imprinting not always benefits the binding properties of the resultant MIPs, which is of significant importance for the rational use of CRPs in generating MIPs with improved properties.

The first combined use of atom transfer radical polymerization (ATRP) and precipitation polymerization in the molecular imprinting field is described. The utilized polymerization technique, namely atom transfer radical precipitation poly- merization (ATRPP), provides MIP microspheres with obvious molecular imprinting effects towards the template, fast template binding kinetics and an appreciable selec- tivity over structurally related compounds. The living chain propagation mechanism in ATRPP results in MIP spherical particles with diameters (number-average diame- ter Dn � 3 lm) much larger than those prepared via traditional radical precipitation polymerization (TRPP). In addition, the MIP microspheres prepared via ATRPP have also proven to show significantly higher high-affinity binding site densities on their surfaces than the MIP generated via TRPP, while the binding association constants Ka and apparent maximum numbers Nmax of the high-affinity sites as well as the specific template bindings are almost the same in the two cases. V C 2009 Wiley

High-throughput experimentation (HTE) was successfully applied in atom transfer radical polymn. (ATRP) of Me methacrylate (MMA) for the rapid screening and optimization of different reaction conditions. A library of 108 different reactions was designed for this purpose, which used four different initiators [ethyl 2-bromoisobutyrate, Me 2-bromopropionate, (1-bromoethyl)benzene, and p-toluenesulfonyl chloride], five metal salts (CuBr, CuCl, CuSCN, FeBr2, and FeCl2), and nine ligands (2,2'-bipyridine and its derivs.). The optimal reaction conditions for Cu(I) halide, CuSCN, and Fe(II) halide-mediated ATRP systems with 2,2'-bipyridine and its 4,4'-dialkyl-substituted derivs. as ligands were detd. Cu(I)-mediated systems were better controlled than Fe(II)-mediated ones under the examd. conditions. A bipyridine-type ligand with a crit. length of the substituted alkyl group (i.e., 4,4'-dihexyl 2,2'-bipyridine) exhibited the best performance in Cu(I)-mediated systems, and p-toluenesulfonyl chloride and Et 2-bromoisobutyrate could effectively initiate Cu(I)-mediated ATRP of MMA, resulting in polymers with low polydispersities in most cases. Besides, Cu(I) halide-mediated ATRP with 4,5'-dimethyl 2,2'-bipyridine as the ligand and p-toluenesulfonyl chloride as the initiator proved to be better controlled than those with 4,4'-dimethyl 2,2'-bipyridine as the ligand, and polymers with much lower polydispersities were obtained in the former cases. This successful HTE example opens up a way to significantly accelerate the development of new catalytic systems for ATRP and to improve the understanding of structure-property relationships of the reaction systems

The controlled atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) catalyzed by iron halide/N-(n-hexyl)-2-pyridylmethanimine (NHPMI) is described. The ethyl 2-bromoisobutyrate (EBIB)-initiated ATRP with [MMA] 0 /[EBIB] 0 /[iron halide] 0 /[NHPMI] 0 = 150/1/1/2 was better controlled in 2-butanone than in p-xylene at 90 °C. Initially added iron(III) halide improved the controllability of the reactions in terms of molecular weight control. The p-toluenesulfonyl chloride (TsC1)-initiated ATRP were uncontrolled with [MMA] 0 /[TsCl] 0 /[iron halide] 0 /[NHPMI] 0 = 150/1/1/2 in 2-butanone at 90 °C. In contrast to the EBIB-initiated system, the initially added iron(III) halide greatly decreased the controllability of the TsCl-initiated ATRP. The ration of iron halide to NHPMI significantly influenced the controllability of both EBIB and TsCl-initiated ATRP systems. The ATRP with [MMA] 0 /[initiator] 0 /[iron halide] 0 /[NHPMI] 0 = 150/1//1/2 provided polymers with PDIs ≥ 1.57, whereas those with [iron halide] 0 /[NHPMI] 0 = 1 resulted in polymers with PDIs as low as 1.35. Moreover, polymers with PDIs of approximately 1.25 were obtained after their precipitation from acidified methanol. The high functionality of the halide end group in the obtained polymer was confirmed by both 1 H NMR and a chain-extenstion reaction. Cyclic voltammetry was utilized to explain the differing catalytic behaviors of the in situ-formed complexes by iron halide and NHPMI with different molar ratios.

The homogeneous atom transfer radical polymerization (ATRP) of n-butyl acrylate with CuBr/N-(n-hexyl)-2-pyridylmethanimine as a catalyst and ethyl 2-bromoisobutyrate as an initiator was investigated. The kinetic plots of ln([M]0/[M]) versus the reaction time for the ATRP systems in different solvents such as toluene, anisole, N,N-dimethylformamide, and 1-butanol were linear throughout the reactions, and the experimental molecular weights increased linearly with increasing monomer conversion and were very close to the theoretical values. These, together with the relatively narrow molecular weight distributions (polydispersity index ∼ 1.40 in most cases with monomer conversion > 50%), indicated that the polymerization was living and controlled. Toluene appeared to be the best solvent for the studied ATRP system in terms of the polymerization rate and molecular weight distribution among the solvents used. The polymerization showed zero order with respect to both the initiator and the catalyst, probably because of the presence of a self-regulation process at the beginning of the reaction. The reaction temperature had a positive effect on the polymerization rate, and the optimum reaction temperature was found to be 100 °C. An apparent enthalpy of activation of 81.2 kJ/mol was determined for the ATRP of n-butyl acrylate, corresponding to an enthalpy of equilibrium of 63.6 kJ/mol. An apparent enthalpy of activation of 52.8 kJ/mol was also obtained for the ATRP of methyl methacrylate under similar reaction conditions. Moreover, the CuBr/N-(n-hexyl)-2-pyridylmethanimine-based system was proven to be applicable to living block copolymerization and living random copolymerization of n-butyl acrylate with methyl methacrylate. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3549–3561, 2002

9-(Guanidinomethyl)anthracene derivatives with a bromo (6) or a vinyl group (10) at the 10-position have been prepared starting from 9-bromoanthracene (1). They show 1:1 complexation with carboxylic acids or carboxylates with K-values of 1.2–1.4×105 M−1 in deuteriomethanol. Copolymerization of 9-vinylanthracene, 9-(guanidinomethyl)-10-vinylanthracene hydrochloride (10), and the 1:1 complex of 10 and ammonium benzoate with ethyleneglycol dimethacrylate (EDMA) gave the polymers in 77–92% yield.