Activators Regenerated By Electron Transfer Atom Transfer Radical Polymerization Research Articles

Construction of antifouling zwitterionic coatings on polypropylene microporous membranes via N-hydroxyphthalimide(NHPI) catalysis

Developing polyolefin microporous membranes with good antifouling ability and high separation efficiency is an important and urgent work. Herein, polypropylene microporous membranes (PP (mm)) containing zwitterionic polymer was prepared by grafting poly (sulfobetaine methacrylate) (PSBMA) onto the membrane via N-hydroxyphthalimide(NHPI) catalysis and activators regenerated by electron transfer atom transfer radical polymerization (ARGET-ATRP) for the first time. The structure, morphology, hydrophilicity and antifouling ability of PP (mm)-g-PSBMA was systematically studied. Water contact angle of the modified membrane could be sharply reduced at a proper grafting degree (GD), and it exhibited extraordinary hydrophilicity. The PP (mm)-g-PSBMA membrane also showed excellent protein antifouling ability and higher water flux compared to that of pristine PP membrane. Flux recovery ratio (FRR) of PP (mm)-g-PSBMA was increased to 93.1 % and relative flux reduction ratio (RFR) was decreased to 25.3%. This work presents a controllable and high efficiency strategy to polyolefin separation membrane for high value products.

Thermoresponsive Reversible Unimer Micelles of Amphiphilic Fluorinated Copolymers

AbstractAmphiphilic fluorinated copolymers PEGMAx‐co‐FAy and TEGMAx‐co‐FAy are prepared by activators regenerated by electron transfer atom transfer radical polymerization (ARGET‐ATRP). All polymers present a reversible thermoresponsive lower critical solution temperature‐type behavior, and a cloud point temperature (Tc) in the range of 30–60 °C strictly dependent on the length of the oxyethylene side chain, the content of the hydrophobic counits, and the concentration of the solution. Combined small angle X‐ray scattering (SAXS) and dynamic light scattering measurements are used to study the self‐assembly behavior in water, organic solvents (tetrahydrofuran [THF] and dimethylformamide [DMF]), and a fluorinated solvent (hexafluorobenzene [HFB]). SAXS confirms the formation of compact‐globular single‐chain self‐folded unimer micelles in water below Tc, which generally presents small hydrodynamic diameters (Dh ≤ 8 nm) as a result of the folding of the hydrophobic perfluorohexylethyl acrylate counits. The copolymers are also able to form reverse unimer micelle in HFB. The copolymers are not able to self‐assemble in unimer micelles in THF or DMF solutions, in which they adopt conventional random coil conformations.

Modification of cellulose nanocrystals via surface-initiated ARGET ATRP and their reinforcement of poly(lactic acid)-based biocomposites

In order to improved the thermal stability and compatibility between cellulose nanocrystals (CNCs) and poly(lactic acid) (PLA), using activators regenerated by electron transfer (ARGET) atom transfer radical polymerization (ATRP), customized functionalization of CNCs was achieved by surface grafting of poly(butyl acrylate) (PBA). PLA nanocomposites with different amounts of nanofillers (ranging from 1 to 5 wt%) was processed via hot-press approach. After the modification, the initial contact angle of nanocellulose increased from 50° to 120°, and the initial thermal degradation temperature increased from 150 °C to 270 °C. SEM revealed that modified CNCs were dispersed uniformly throughout the PLA matrix. The thermal characteristics of PLA composites reinforced with PBA-grafted CNCs were analyzed using DSC , demonstrating that the modified CNCs and PLA matrix had improved interactions. The compatibility of modified CNCs with the matrix was enhanced as a consequence of surface modified CNCs having better hydrophobicity and improved thermal stability. Tensile tests were used to evaluate the impact of CNCs on the mechanical characteristics, pointing an increase in the tensile strength, elongation and Young’s Modulus of roughly 350%, 100% and 120%, respectively, at 2 wt% CNC-PBA400 content. • Green composites from poly(lactic acid) and cellulose nanocrystals (CNCs). • Poly(butyl acrylate) grafting helped to disperse CNCs within PLA. • CNCs influenced the crystallization characterization and physico-mechanical properties of PLA.

ARGET ATRP of Methyl Acrylate and Methyl Methacrylate with Diazocine-Derived Initiators

Diazocine-functionalized initiators for atom transfer radical polymerization (ATRP) were synthesized and tested for their efficiency in controlled radical polymerizations of methyl acrylate and methacrylate under reaction conditions for activators regenerated by electron transfer (ARGET). The α-bromoisobutyl condensates of anilide and benzyloxycarbonate required high amounts of reducing agents and catalysts for the initiation. On the other hand, violet light irradiation during ATRP caused severe retardation or termination during initiation of the anilide compound, in contrast to the previously reported photoinduced initiation under otherwise very similar conditions. The final linear elastomers obtained from optimized polymerization kinetics responded to light irradiation of 405 and 525 nm wavelengths by Z/E photoisomerization of diazocine in both solution and in the solid state. The E → Z thermal relaxation rate was highly influenced by electronic effects on the diazocine ring, the solvent, and the polymer matrix in the solid state. Our polymers find potential use as photonic materials in ultraviolet light sensors and optical waveguides.

Synthesis of N‐Substituted Maleimides and Poly(styrene‐co‐N‐maleimide) Copolymers and Their Potential Application as Photoresists

AbstractPoly(styrene‐co‐N‐maleimide) copolymers bearing tert‐butoxycarbonyl (t‐BOC)‐protected amine groups attached to side chains of varying lengths are synthesized via activators regenerated by electron transfer atom transfer radical polymerization (ARGET‐ATRP) and investigated from the perspective of photoresist applications. The length of the alkyl substituents enables control of thermal properties as well as hydrophobicity, which are critically important for resist processing. Removal of the acid labile t‐BOC group during deep‐UV (DUV)exposure shifts solubility in the exposed areas and well‐defined line space patterns of 1 µm are obtained for the selected copolymers. The correlation between glass transition temperature (Tg) and solubility contrast determines the lithographic performance where the copolymers with shorter alkyl chains exhibit promising results.

Polyethylene glycol-based RAFT agent cum ATRP macroinitiator initiated block copolymerization of methyl methacrylate

PMMA-b-PEG-b-PMMA block copolymer has been synthesized by the activators regenerated by electron transfer atom transfer radical polymerization (ARGET-ATRP) of methyl methacrylate (MMA) using modified polyethylene glycol (PEG) as initiator. PEG is chemically modified by CS2 followed by an esterification to incorporate initiating sites for ATRP as well as for RAFT polymerization. The prepared macroinitiator has been characterized by FT-IR and NMR analyses for its structural validation. FT-IR and NMR analyses confirmed the successful synthesis of the macro initiator. This macro initiator has been used to prepare ABA type triblock copolymer with MMA via ARGET-ATRP. The polymerization reaction is carried out using cupric bromide (CuBr2) as catalyst in combination with N,N,N′,N″,N″-pentamethyl diethylenetriamine (PMDETA) as ligand in N, N dimethyl formamide (DMF) at 70C. Ascorbic acid is used as reducing agent. The conversion of the monomer was calculated gravimetrically. The successful preparation of the block copolymer is confirmed by FT-IR, 1H NMR and 13C NMR analyses. The MALDI-TOF mass analysis of the block copolymers also confirm the presence of monomer MMA, dithionate and PEG parts in the block copolymer. The purified block copolymer is analyzed by TGA, and SEM analyses. TGA analysis shows that the prepared block copolymer has better (Tmax = 366C) thermal stability than the PMMA (Tmax = 349C) homopolymer.

Preparation of LCST regulable DES-lignin-g-PNVCL thermo-responsive polymer by ARGET-ATRP

To expand the field of high-value utilization of lignin. The degraded deep eutectic solvent lignin-grafted poly (N-Vinyl caprolactam) (DES-lignin-g-PNVCL) was synthesized by modified DES-lignin and NVCL via the combination of activators regenerated by electron transfer-atom transfer radical polymerization (ARGET-ATRP). Fourier transform infrared spectroscopy (FT-IR), 1H NMR, X-ray electron spectroscopy (XPS), dynamic light scattering (DLS), differential scanning calorimeter (DSC) were used to characterize the structure and performance of DES-lignin-g-PNVCL. The results indicated that the PNVCL and DES-lignin-g-PNVCL were successfully prepared by ARGET-ATRP. The lowest critical solution temperature (LCST) of PNVCL was 35.75 °C. Due to different strength of hydrogen bond, different energies were required, so the LCST of the polymer can be regulated. When the molar ratio of phenolic hydroxyl group in degraded DES-lignin to 2-bromoisobutyryl bromide (BiBB) was increased from 1:1 to 1:7, the grafting rate of DES-lignin-Br was increased from 32.87% to 60.84%, and the LCST of DES-lignin-g-PNVCL was decreased from 47.98 °C to 27.88 °C. The LCST of DES-lignin-g-PNVCL was increased from 30.98 °C to 44.64 °C when the addition amount of DES-lignin-Br was increased from 20 mg to 200 mg. The LCST of DES-lignin-g-PNVCL was increased from 27.20 °C to 39.86 °C when the ratio of DMF/water was increased from 1:4 to 4:1. The LCST of DES-lignin-g-PNVCL was decreased from 52.10 °C to 31.02 °C when the concentration of DES-lignin-g-PNVCL was increased from 0.5 mg/mL to 2.5 mg/mL. The equation represented the relationship between LCST and influencing factors was obtained, the good predictability provided a tactics for preparing desired LCST thermo-responsible polymer.

Copper-catalyzed ARGET ATRP of styrene from ethyl α-haloisobutyrate in EtOAc/EtOH, using ascorbic acid/Na2CO3 as reducing system

Atom transfer radical polymerization (ATRP) is one of the most powerful techniques to synthesize precisely tailored polymers and macrostructures. Activators regenerated by electron transfer (ARGET) ATRP was developed as a “green” strategy to decrease the load of the metal catalyst. However, ARGET ATRP usually uses not-so-green reducing agents (e.g. Sn2+) or expensive and industrially impractical procedures. For these reasons, we report an ARGET ATRP of styrene with various carbonates as reducing agents, both alone and paired with ascorbic acid (AA), using monofunctional initiators and Cl or Br as exchanging atoms. The solvent mixture is composed of the green combination of EtOAc and EtOH, even in the presence of modest amounts of H2O. Cyclic voltammetry was used to evaluate the effect of H2O on the catalyst, as well as the absence of AA. The system returned high yields and low dispersities with low amounts of catalyst (~60 ppm) and moderate reaction times. Excellent results were obtained only with the Cl-ATRP system. NMR spectroscopy and kinetic analyses proved the livingness of the final polymer chains.

Construction of antifouling fluorinated polymer brush via activators regenerated by electron transfer ATRP and thiol-epoxy click reaction

In this work, fluorine containing polymer brushes was grafted on the functionalized stainless steel (SS) by activators regenerated by electron transfer atom transfer radical polymerization (ARGET-ATRP) and thiol-epoxy click reaction. PGMA brushes would be grafted on SS by coating the sheets with brominated polydopamine (PDA) as a reactive under-layer, and subsequently surface-initiate ARGET-ATRP of glycidyl methacrylate (GMA). Then the short-fluorinated alkyl chains were anchored on the PGMA backbones based on the click reaction between epoxy groups of PGMA and 1H, 1H, 2H, 2H-perfluorodecanethiol (PFDT), which endowed the surfaces of the polymers with low surface free energy. The surface compositions and morphologies of the functionalized SS have been characterized by attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM) and atomic force microscopy (AFM). The results of water contact angle analysis exhibited high hydrophobicity of the fluorinated polymer grafting modified SS surface. Bovine serum albumin (BSA) resistance performance of the functionalized SS was evaluated by BCA protein assay reagent, fluorescence microscope and XPS. The results exhibited that grafting fluoropolymer brushes modified SS with lower protein adsorption compared with the pristine SS surface, which might be served as promising environmentally friendly polymer antifouling coatings.

Hemocompatibility of polyzwitterion-modified titanium dioxide nanotubes

Titanium dioxide nanotubes (TNTs) have attracted increasing interest as implantable materials due to their many desirable properties. However, their blood compatibility remains an issue. In this paper, TNTs of different diameters were modified with two types of zwitterionic polymers, poly(sulfobetaine methacrylate) (pSBMA) and poly(carboxybetaine methacrylate) (pCBMA), which were grafted onto the TNTs using ARGET-ATRP (activators regenerated by electron transfer atom transfer radical polymerization) method. Both pSBMA and pCBMA brushes coatings were found to greatly reduce adsorption of bovine serum albumin (BSA) and fibrinogen (Fib) onto the TNTs, showing excellent protein resistance. Moreover, the effects of the surface topography on the amount of protein adsorption were largely suppressed by the polyzwitterion coatings. The conformation of the protein adsorbed to the substrates was analyzed at the molecular level by Fourier-transform infrared reflection spectroscopy (FT-IR), which revealed that the BSA adsorbed on the polyzwitterion-modified TNTs adopted significantly different secondary structures from that on the virgin TNTs, whereas the conformation of the adsorbed Fib remained basically the same. The polyzwitterion-modified TNTs were found to be non-hemolytic, and platelet adhesion and activation was significantly reduced, showing excellent blood compatibility.

Surface tailoring of polypropylene separators for lithium-ion batteries via N-hydroxyphthalimide catalysis

Surface modification of polyolefine separators for high performance lithium-ion batteries has been a worthwhile research topic. In this work, poly (poly (ethylene glycol) methacrylate) (PPEGMA) was firstly grafted onto polypropylene (PP) separator based on N-hydroxyphthalimide (NHPI) catalysis and activators regenerated by electron transfer atom transfer radical polymerization (ARGET-ATRP). Bis(2,2,2-trichloroethyl) azodicarboxylate (BTCEAD) was anchored on the surface of PP separators in the presence of NHPI. Then BTCEAD functionalized PP separator initiated the polymerization of PEGMA by ARGET-ATRP. Thus, structure controllable PPEGMA was grafted on the surface of PP separators. The results of contact angle and electrolyte uptake tests demonstrated that electrolyte wettability of PPEGMA functionalized PP separator has been significantly improved. Electrochemical measurements indicated that the ionic conductivity and discharge capacity retention of cells assembled with PPEGMA functionalized PP separators were distinctly higher than that of cells with pristine PP separator. Herein, we presented a new methodology with high efficiency to modify PP separators under mild condition, which was also applied to other polyolefine separator for high performance lithium-ion batteries. The proposed approach might have many other potential applications in membrane modification field.

Investigation of the LCST-Thermoresponsive Behavior of Novel Oligo(Ethylene Glycol)-Modified Pentafluorostyrene Homopolymers

Amphiphilic tetrafluorostyrene monomers (EFS8) carrying in the para position an oligoethylene glycol chain containing 8 oxyethylenic units on average were synthesized and used for preparation via activator regenerated by electron transfer atom transfer radical polymerization (ARGET-ATRP) of the corresponding amphiphilic homopolymers (pEFS8-x) with different degrees of polymerization (x = 26 and 46). Combining light transmittance and nano-differential scanning calorimetry (n-DSC) measurements revealed that pEFS8-x homopolymers displayed a lower critical solution temperature (LCST) thermoresponsive behavior in water solutions. Moreover, n-DSC measurements revealed the presence in heating scans of a broad endothermic peak ascribable to the dehydration process of the polymer single chains (unimers) and their collapse into aggregates. Consistently, dynamic light scattering (DLS) measurements showed below the LCST the presence of small nanostructures with a hydrodynamic diameter size Dh of 6–7 nm, which collapsed into concentration-dependent larger multichain aggregates (Dh = 300–3000 nm) above LCST. Interestingly, n-DSC data showed that the unimer-aggregate transition was reversible up to a specific temperature (Trev) of each homopolymer, which in any case was higher than Tmax. When heating above Trev the transition was no longer reversible, causing the shift of Tonset and Tmax at lower values, thus suggesting an increase in hydrophobicity of the polymer systems associated with a temperature-dependent dehydration process.

Green and sustainable method of manufacturing anti-fouling zwitterionic polymers-modified poly(vinyl chloride) ultrafiltration membranes

The nonsolvent induced phase separation (NIPS) method for ultrafiltration (UF) membrane fabrication relies on the extensive use of traditional solvents, thus ranking first in terms of ecological impacts among all the membrane fabrication steps. Methyl-5-(dimethylamino)-2-methyl-5-oxopentanoate (PolarClean), as a green solvent, was utilized in this study to fabricate poly(vinyl chloride) (PVC) UF membranes. Subsequently, in post-treatment process, zwitterionic polymer, [2-(methacryloyloxy) ethyl] dimethyl-(3-sulfopropyl) ammonium hydroxide (DMAPS), was grafted onto the membrane surface to enhance its anti-fouling properties using a greener surface-initiated activator regenerated by electron transfer-atom transfer radical polymerization (ARGET-ATRP) reaction. This novel method used low toxicity chemicals, avoiding the environmental hazards of traditional ATRP, and greatly improving the reaction efficiency. We systematically studied the grafting time effect on the resulted membranes using sodium alginate as the foulant, and found that short grafting time (30 min) achieved excellent membrane performance: pure water permeability of 2872 L m−2 h−1 bar−1, flux recovery ratio of 86.4% after 7-hour fouling test, and foulant rejection of 96.0%. This work discusses for the first time the greener procedures with lower environmental impacts in both fabrication and modification processes of PVC UF membranes.

Valorization of organosolv lignin: Architectural strategy to enhance mechanical strength and UV protection in self-healing polymers

Altering the architecture of conventional self-healing polymers, from the original linear to a multiple-branched structure, has proved to be efficient in improving the mechanical properties. A novel strategy to achieve similar results is to utilize organosolv lignin, a renewable biopolymer with rigid aromatic backbone that has multiple active sites amenable for grafting heterogenous polymer units. In this study, a lignin-based triblock copolymer, namely lignin-grafted poly(diacetone acrylamide-co-2-hydroxypropyl acrylate) or LPDH, was successfully synthesized via ARGET-ATRP (activator regenerated by electron transfer-atom transfer radical polymerization) mechanism. The LPDH copolymers were found to exhibit higher ultimate tensile stress (≤6.3 ± 1.4 MPa) and Young’s modulus (194.2 ± 46.1 MPa), as well as significant (86 %) recovery of tensile strength and extensibility. Moreover, the LPDH copolymers could absorb UV radiation. Since, a commercially available organosolv lignin was directly utilized to prepare the copolymer without any purification, it is suggested that LPDH has potential to be manufactured on an industrial scale for self-healing, anti-UV coating applications. It also is hoped that the proposed synthetic strategy will inspire the development of renewable biomass-based polymers with similar functions.

Thermoresponsive Cationic Block Copolymer Brushes for Temperature-Modulated Stem Cell Separation.

Recently, cell separation methods have become important for preparing cells for transplantation therapy. In this study, a thermoresponsive cationic block copolymer brush is developed as an effective cell separation tool. This brush is prepared on glass surfaces using two steps of activator regenerated by electron transfer-atom transfer radical polymerization (ARGET-ATRP). The cationic segment is prepared in the first step of the ARGET-ATRP of N,N-dimethylaminopropylacrylamide (DMAPAAm). In the second step, the thermoresponsive segment is prepared, attached to the bottom cationic segment, through ARGET-ATRP with N-isopropylacrylamide (NIPAAm). The cell adhesion behavior of the prepared thermoresponsive cationic copolymer, PDMAPAAm-b-PNIPAAm, brush is observed using umbilical cord-derived mesenchymal stem cells (UCMSC), fibroblasts, and macrophages. At 37 °C, all three types of cells adhere to the thermoresponsive cationic copolymer brush. Then, by reducing the temperature to 20 °C, the adhered UCMSC are detached from the copolymer brush, whereas the fibroblasts and macrophages remain adhered to the copolymer brush. Using this copolymer brush, UCMSC can be purified from the cell mixture simply by changing the temperature. Therefore, the prepared thermoresponsive cationic copolymer brush is useful as a cell separation tool for the purification of mesenchymal stem cells.

Investigation of microstructure in poly(methyl methacrylate) prepared via ambient temperature ARGET-ATRP: a combined approach of 1D and 2D NMR spectroscopy

This investigation reports the analysis of different microstructures present in poly(methyl methacrylate) (PMMA) using1D and 2D NMR spectroscopy. The PMMA used in this study has been prepared via activators regenerated by electron transfer atom transfer radical polymerization (ARGET-ATRP) in DMF at ambient temperature using methyl 2-chloro propionate (MCP) as initiator, CuBr2 as catalyst in combination with N, N, N´, N´´, N´´- pentamethyldiethylenetriamine (PMDETA) as ligand and ascorbic acid as reducing agent.13C NMR, which provides good information about tacticity of a polymer, has been used extensively along with 1H NMR spectroscopy to extract the information about the different microstructures present in PMMA. Heteronuclear multiple-bond correlation (HMBC), heteronuclear single-quantum coherence (HSQC), and total correlation spectroscopy (TOCSY) were also used to study the position of protons, couplings with carbon etc. in the PMMA.

Regulating Gelation Time and Kinetics Analysis Based on the ARGET ATRP Mechanism

ABSTRACTA novel activators regenerated by electron transfer (ARGET) atom transfer radical polymerization (ATRP) initiation system composing of an initiator sodium chloroacetate, a catalyst ferric chloride, and a reducing agent ascorbic acid was developed to improve the gelation time of the in situ crosslinked polymer system. The kinetics of polymerization of acrylamide showed features of a living/controlled process in which the concentrations of the growing radicals [P·] are kept constant throughout the polymerization process. Compared with conventional potassium persulfate initiators, the gelation time of the in situ crosslinked polymer system can be improved to 40 h or even longer using the ARGET ATRP initiation system at 80 °C due to the low radical concentration and slow polymerization reaction. Core flooding test showed that the ARGET ATRP initiating system developed could initiate the polymerization reaction of the in situ crosslinked polymer system in the core. However, the gelation time was extended in comparison to that of the result obtained in the bottle, resulting from the dilution and adsorption of ARGET ATRP components during the injection process. The research expands the application field of the ARGET ATRP principle and has a promising prospect on controlling the gelation time of the in situ crosslinked polymer system. © 2020 Wiley Periodicals, Inc. J. Polym. Sci. 2020, 58, 519–527

Ferrocene-integrated conjugated microporous polymer nanosheets: Active and regenerative catalysts for photomediated controlled radical polymerization

The challenge of light-driven controlled radical polymerization through non-noble metal catalyst remains the most significant issue. Ferrocene-bearing microporous aromatic polymer nanosheets (termed “FeMAP-11”) that feature high chemical stability were reported here to synergistically combine the advantageous properties of the redox-active ferrocene units and the conjugated microporous polymers (CMPs), and to be able to serve as photocatalyst for activators regenerated by electron transfer atom transfer radical polymerization (AGET-ATRP). It succeeded in initiating polymerizations of 3 common vinyl monomers, i.e. methyl methacrylate (MMA), methacrylate (MA) and styrene (St), and produced polymers with controlled molecular weight and relatively low molecular weight dispersity (˜1.3). Benefiting from steric hindrance through ketone-amine chemistry, the microporous catalyst with tolerance to acidic and basic media was found stable under the AGET-ATRP conditions. It showed negligible metal leaching and good recyclability for at least 10 cycles without sacrifice of its catalytic performance. Our tests proved that FeMAP-11 exceeded the state-of-the-art ATRP photocatalysts such as UiO-66-NH2, titanium MOF-901 and the commercial P-25 Titania, demonstrating promising potential in catalysis in view of green chemistry.

Thermoresponsive anionic copolymer brush-grafted surfaces for cell separation

Cell separation methods that do not require surface modification of cells are needed in tissue engineering and regenerative medicine. We developed thermoresponsive anionic polymer brushes for cell separation without modification of the cell surfaces. Copolymer brush poly(N-isopropylacrylamide-co-N-tert-butylacrylamide-co-tert-butyl acrylate, P(NIPAAm-co-tBAAm-co-tBA), was prepared on a cover glass plate through activator regenerated by electron transfer atom transfer radical polymerization (ARGET-ATRP). The tert-butyl group of the copolymer brush was then deprotected and a P(NIPAAm-co-tBAAm-co-acrylic acid (AAc)) brush-modified glass surface was obtained. ARGET-ATRP synthesis achieved polymers with low polydispersity. The negative surface charge of the polymer brush-modified substrates was evaluated using zeta potential measurements and the phase transition temperature of the polymer was modulated between 37–20 °C to perform cell adhesion and detachment, respectively. The adhesion and detachment behavior of cells used in cardiovascular tissue engineering on the thermoresponsive anionic polymer brushes was investigated. Normal human umbilical vein endothelial cells (HUVEC) exhibited prompt detachment from the thermoresponsive anionic polymer brush surfaces. In addition, normal human aortic smooth muscle cells (SMC) exhibited relatively high adhesion on thermoresponsive anionic polymer brush-modified surfaces compared with those modified with thermoresponsive polymer brushes without anionic groups. By utilizing the difference in the cell adhesion and detachment properties of the cell types, a mixture of HUVEC and SMC was separated simply by altering the applied temperature. This result indicated that the prepared thermoresponsive anionic polymer brush-modified glass surface could be used as a tool for the separation of cells in cardiovascular tissue engineering.

High retreatability and dimensional stability of polymer grafted waterlogged archaeological wood achieved by ARGET ATRP

To explore new methods to maintain the dimensional stability of waterlogged archaeological wood after drying and keep the natural cell lumens unaltered for future retreatments, activator regenerated by electron transfer (ARGET) atom transfer radical polymerization (ATRP) is employed to consolidate archaeological wood. To prepare the ATRP process, the waterlogged archaeological wood samples (Pinus massoniana with maximum moisture content of around 529%) were first modified by 2-bromoisobutyryl bromide in CH2Cl2 to acquire C-Br bonds as initiators. Then, butyl methacrylate or styrene was polymerized to the remaining cell walls with catalyst (CuBr2), reductant (ascorbic acid) and ligand (PMDETA) in ethanol. After the treatment, the samples were washed and naturally dried. The results characterized by microscopy showed that the polymerization only took place within the remaining cell walls, showing no sign of collapse or distortion after air drying, and all natural cell lumens could be retained for future retreatments. Also, anti-shrinkage efficiencies as high as 87.8% for the wood sample grafted with polystyrene and 98.5% for the wood sample grafted with polybutylmethacrylate were obtained from the treatment described in this paper, indicating modification of grafting polymer through ARGET ATRP can help maintain the dimensional stability of water archaeological wood effectively.