Oligo(ethylene Glycol) Methyl Ether Methacrylate Research Articles

Mechanical properties of temperature-responsive gels containing ethylene glycol in their side chains.

The mechanical properties of temperature-responsive and biocompatible poly(oligo-ethylene glycol methyl ether methacrylate)-based gels were investigated using dynamic viscoelasticity measurements so as to find applications in tissue and biomedical engineering. The gels were copolymerized using two ethylene glycol methacrylate monomers with diethylene glycol side chains: diethylene glycol methacrylate (MeO2MA), which contains two ethylene oxide units, and oligo-ethylene glycol methyl ether methacrylate (OEGMA) with either four or five ethylene oxide units. The storage (G') and loss (G'') moduli of these gels exhibit unique temperature-responsive behavior and depend on the copolymerization ratio. In MeO2MA-rich gels, phase separation occurred with increasing temperature, resulting in a significant increase in G' and the disappearance of the frequency dependence of G''. Although phase separation of OEGMA-rich gels was also observed with increasing temperature, it resulted in only a slight increase in the storage modulus due to the steric hindrance of the side chain. The mechanical properties of these gels are thus found to be strongly affected by a slight difference in the number of ethylene oxide groups in their side chains.

Gradient Polymerization-Induced Self-Assembly: A One-Step Approach.

In this work, the authors report a novel single-step, one-pot process for the synthesis of self-assembled nanoparticles using a polymerization-induced self-assembly (PISA) mechanism. In contrast to conventional approaches employing a pre-formed macromolecular stabilizer, the disparate reactivities between two monomers, oligo(ethylene glycol) methyl ether methacrylate (OEGMA) and diacetone acrylamide (DAAm), are exploited instead to synthesize a gradient copolymer directly in aqueous solution. Due to the hydrophobicity of poly(DAAm), these gradient copolymers can self-assemble in situ to form spheres and worms stabilized by the OEGMA residues. A surprisingly broad range of parameters are identified in which the worm morphology can be stabilized, which is highlighted by significant gelation of the reaction mixture in situ. This single-step gradient copolymerization approach to PISA is more efficient than conventional two-step syntheses. These results demonstrate improved reproducibility owing to the production of self-assembled nanoparticles directly in a one-pot and single-step synthesis.

Access to Photoreactive Core‐Shell Nanomaterials by Photoinitiated Polymerization‐Induced Self‐Assembly

AbstractWe report the straightforward synthesis of photoreactive nanoobjects exhibiting various colloidal morphologies by photoinitiated polymerization‐induced self‐assembly (PISA). Poly(oligoethylene glycol methyl ether methacrylate) copolymers with pendent UV‐activatable diaryl tetrazole moieties were employed as macromolecular chain‐transfer agents in water for the dispersion photopolymerization of 2‐hydroxypropyl methacrylate under visible light. This led to the in situ formation of amphiphilic block copolymers, driving the self‐assembly into core‐shell nanoparticles, nanofibers, and nano/microvesicles. The tetrazole group present in the shell of the nanoobjects permitted functionalization with various functional molecules and polymers via UV‐triggered nitrile imine‐mediated tetrazole–ene cycloaddition (NITEC), enabling the alteration of surface properties of the nanomaterials (fluorescence, charge, hydrophilicity).

Core‐crosslinking as a pathway to develop inherently antibacterial polymeric micelles

ABSTRACTPositively charged polymeric materials have been an alternative to combat bacteria as they exhibit inherently antibacterial potency via bacteria membrane disruption. In this study, we report facile preparation of positively charged core‐crosslinked polymeric micelles with inherent antibacterial properties. Spherical micelles were prepared by self‐assembling of poly(4‐vinylpyridine)‐b‐(oligoethylene glycol methyl ether methacrylate) copolymer in aqueous solution. Herein, quaternization reaction was utilized for the first time to core crosslink the micelles through the pyridine rings utilizing their hydrophobic core and thus resulting positively charged nanostructures. Dynamic light scattering (DLS) results identified that the micelles have an average hydrodynamic diameter of 114 nm with a polydispersity index ranging between 0.105 and 0.114. The electrophoretic light scattering (ELS) measurements demonstrated that the micelles have zeta potential values ranging from +38 to +63 mV. It was evident from both ELS and DLS results that the micelles in solution exhibit long‐term stability as the samples were able to maintain their size and charge even after a year of storage. Further, the micelles exhibited inherently antibacterial activity against Escherichia coli and furthermore, this antibacterial efficacy was sustained over a period of 1 year. These stable core‐crosslinked micelles are proposed to have great potential as antibacterial materials for long‐term applications. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48393.

The crucial role of macromolecular engineering, drug encapsulation and dilution on the thermoresponsiveness of UCST diblock copolymer nanoparticles used for hyperthermia

Poly(acrylamide-co-acrylonitrile) (P(AAm-co-AN)), an upper critical solution temperature (UCST)-type copolymer in water, was synthesized by reversible addition fragmentation chain transfer (RAFT) copolymerization and used as a macro-RAFT agent for the polymerization of oligo(ethylene glycol) methyl ether methacrylate (OEGMA) to yield amphiphilic diblock P(AAm-co-AN)-b-POEGMA copolymer. A series of copolymers with different AN content was obtained allowing to finely tune the UCST behavior (cloud point (Tt-UCST) from 35 to 78 °C). Addition of the POEGMA block did not modify the Tt-UCST regardless its Mn but provided a lower critical solution temperature behavior at high temperature. Nanoparticles were then formulated by the nanoprecipitation technique revealing that copolymers with higher Tt-UCST yield smaller, better-defined nanoparticles. Eventually, doxorubicin (Dox) was encapsulated into nanoparticles made from the copolymer having a Tt-UCST close to mild hyperthermia (~43 °C). Surprisingly, Dox encapsulation increased Tt-UCST and gave smaller nanoparticles as opposed to their unloaded counterparts. The dilution of the suspension also led to a decrease of Tt-UCST. No obvious hyperthermia effect was observed on the cytotoxicity of Dox-loaded nanoparticles. Our study highlighted the influence of macromolecular engineering, drug encapsulation and nanoparticle dilution on UCST behavior, important features often overlooked despite their crucial impact in the development of thermosensitive nanoscale drug delivery systems.

A Remarkably Large Phase‐Transition Effect in a Random Copolymer of Oligo(ethylene glycol) Methyl Ether Methacrylate (OEGMA)500 Induced by the Photochemistry of the 2‐(Hydroxyimino)aldehyde Group

AbstractThe effect of UV irradiation on the cloud points (CP) of aqueous solutions of a random 1:1 copolymer of oligo(ethylene glycol) methyl ether methacrylate (OEGMA500) and a 2‐(hydroxyimino)aldehyde (HIA) functionalized methacrylate is presented. CPs are determined by visible spectroscopy and dynamic light scattering (DLS). 1H and 13C NMR experiments are carried out in D2O and DMSO‐d6 on the polymer and on an HIA‐functionalized model of the photoresponsive repeat unit. UV‐irradiated solutions exhibit an unprecedented increase of the phase‐separation temperature for an OEGMA photoresponsive copolymer (10–22 °C, depending on concentration and irradiation conditions). Phase separation is reversible with little hysteresis. With both pristine and irradiated polymer solutions, aggregate dimensions are <10 nm (DLS) at room temperature. Aggregates of >100 nm form at the CP and gradually grow as temperature increases, whereas the light‐induced processes of the repeat unit model in DMSO‐d6 are well identified (e.g., oxime E/Z isomerization and Norrish‐Yang cyclization of the aldehyde moiety), it is not straightforward to extrapolate such behavior to the polymeric solution in water. The remarkably large phototriggered thermal effect in the present work motivates further investigations on the solvent‐dependent photochemistry of HIA as a promising functional group for the synthesis of multi‐stimuli responsive materials.

The synthesis of a new chitosan based superplasticizer and investigation of its effects on concrete properties

Chitosan-g-POEGMA (Chitosan-g-poly[oligo(ethyleneglycol) methyl ether methacrylate]) graft copolymers are prepared by grafting of oligo (ethylene glycol methyl ether) methacrylate (OEGMA) on chitosan via redox free radical polymerization method using ceric ammonium nitrate (CAN) as the initiator at 40 °C. Then the resulting copolymers are sulphated by sulphuric acid, chlorosulfonic acid and fuming sulphuric acid (Oleum). The compounds are characterized by FT-IR, NMR, and Elemental analysis. The chitosan homopolymer is also sulphated to compare the results. Taking all characterization results and water solubility ratios into account, it is decided to conduct tests on concrete specimens containing graft copolymers sulphated with oleum sulfuric.Water-reducing properties in the fresh concrete have been examined. Compared to the reference concrete; it is observed that water-reducing of sulphonated graft is %6 and sulphonated chitosan is %5. The unit weights of the reference concrete is as 2380 kg/m3, sulphonated graft is as 2395 kg/m3 and sulphonated chitosan is as 2388 kg/m3. The air content of the reference concrete is measured as 2%, sulphonated graft as 1.5% and sulphonated chitosan as 1.6%. 28-day concrete durability results are determined as 30.1 MPa for the reference concrete, 34.7 MPa for sulphonated graft and 33.8 MPa for sulphonated chitosan.

Ligand-Binding Cooperativity Effects in Polymer-Protein Conjugation.

We present an electron paramagnetic resonance (EPR) spectroscopic characterization of structural and dynamic effects that stem from post-translational modifications of bovine serum albumin (BSA), an established model system for polymer-protein conjugation. Beyond the typical drug delivery and biocompatibility aspect of such systems, we illustrate the causes that alter internal dynamics and therefore functionality in terms of ligand-binding to the BSA protein core. Uptake of the paramagnetic fatty acid derivative 16-doxyl stearic acid by several BSA-based squaric acid macroinitiators and polymer-protein conjugates was studied by EPR spectroscopy, aided by dynamic light scattering (DLS) and zeta potential measurements. The conjugates were grafted from oligo(ethylene glycol) methyl ether methacrylate (OEGMA), forming an overall core-shell-like structure. It is found that ligand-binding and associated parameters such as binding affinity, cooperativity, and the number of binding sites of BSA change drastically with the extent of surface modification. In the course of processing BSA, the ligands also change their preference for individual binding sites, as observed from a comparative view of their spatial alignments in double electron electron resonance (DEER) experiments. The protein-attached polymers constitute a diffusion barrier that significantly hamper ligand uptake. Moreover, zeta potentials (ζ) decrease linearly with the degree of surface modification in protein macroinitiators and an effective dielectric constant can be estimated for the polymer layer in the conjugates. All this suggests that ligand uptake characteristics in BSA can be fine-tuned by the extent and nature of such post-translational modifications (PTMs). We show that EPR spectroscopy is suitable for quantifying these subtle PTM-based functional effects from self-assembly of substrate and ligand.

Biodegradable Thermomagnetically Responsive Soft Untethered Grippers.

Soft-robotic devices such as polymeric microgrippers offer the possibility for pick and place of fragile biological cargo in hard-to-reach conduits with potential applications in drug delivery, minimally invasive surgery, and biomedical engineering. Previously, millimeter-sized self-folding thermomagnetically responsive soft grippers have been designed, fabricated, and utilized for pick-and-place applications but there is a concern that such devices could get lost or left behind after their utilization in practical clinical applications in the human body. Consequently, strategies need to be developed to ensure that these soft-robotic devices are biodegradable so that they would disintegrate if left behind in the body. In this paper, we describe the photopatterning of bilayer gels composed of a thermally responsive high-swelling poly(oligoethylene glycol methyl ether methacrylate ( Mn = 500)-bis(2-methacryloyl)oxyethyl disulfide), P(OEGMA-DSDMA), and a low-swelling poly(acrylamide- N, N'-bis(acyloyl)cystamine) hydrogel, in the shape of untethered grippers. These grippers can change shape in response to thermal cues and open and close due to the temperature-induced swelling of the P(OEGMA-DSDMA) layer. We demonstrate that the grippers can be doped with magnetic nanoparticles so that they can be moved using magnetic fields or loaded with chemicals for potential applications as drug-eluting theragrippers. Importantly, they are also biodegradable at physiological body temperature (∼37 °C) on the basis of cleavage of disulfide bonds by reduction. This approach that combines thermoresponsive shape change, magnetic guidance, and biodegradability represents a significant advance to the safe implementation of untethered shape-changing biomedical devices and soft robots for medical and surgical applications.

Self-assembly and drug release control of dual-responsive copolymers based on oligo(ethylene glycol)methyl ether methacrylate and spiropyran

To compare the synthesis and drug release of random and block copolymers, random and block copolymerizations of oligo(ethylene glycol)methyl ether methacrylate (OEGMA) and 1′-(2-methacryloxyethyl)-3′,3′-dimethyl-6-nitrospiro-(2H-1-benzopyran-2,2′-indoline) (SPMA) were carried out by atom transfer radical polymerization. The 1H NMR and GPC results indicated the targeted random and block copolymers were successfully synthesized. Critical micelle concentrations of random and block copolymers were determined as 0.0178 mg/mL and 0.0265 mg/mL, and the micelle aggregation numbers of the random and block copolymers were calculated as approximately 17 and 13, respectively, indicating that more molecular chains were required to form a stable polymeric micelle for a random than its block copolymer. A lower critical solution temperature of 37 °C, the human body temperature, was obtained for two copolymer samples, suggesting that they might have potential application in the biomedical field. During the self-assembly, the morphology of block copolymer micelles was more regular than that of random copolymer, and both copolymers exhibited the exchange of hydrophilic and hydrophobic segments called as “Schizophrenic” behavior under UV light irradiation at 50 °C. With doxorubicin as a model molecule in drug release control, heating and ultraviolet light irradiation could accelerate the drug release process to some extent, indicating the potential application of the resulting random and block copolymers in drug release and bioengineering.

Dynamic Fluctuations of Thermoresponsive Poly(oligo-ethylene glycol methyl ether methacrylate)-Based Hydrogels Investigated by Dynamic Light Scattering

The dynamics of thermoresponsive and biocompatible gels was investigated using dynamic light scattering. The gels were copolymerized by two types of ethylene glycol methacrylates having short and long hydrophilic side chains consisting of ethylene oxide units. Their dynamics was decomposed to fast and slow modes. The critical temperature was determined from the fast mode (cooperative diffusion) and was controlled lineally by the copolymerization ratio of the two monomers, which is one of the advantages in the gel system. The formation mechanism of hydrophobic domains in the gels was investigated from the slow mode. The hydrophobic domains grew in the gels by rising temperature, and they were copolymerization ratio dependent. The domain formation was suppressed as the copolymerization ratio of the longer side chain was increased. The results of this study should lead to new design strategy for the bioapplications, including drug delivery systems that require a retention of their smart functions.

Impact of Polymer Bioconjugation on Protein Stability and Activity Investigated with Discrete Conjugates: Alternatives to PEGylation.

Covalent attachment of synthetic polymers to proteins, known as protein-polymer conjugation, is currently one of the main approaches for improving the physicochemical properties of these biomolecules. The most commonly employed polymer is polyethylene glycol (PEG), as evidenced by extensive research and clinical track records for its use in biopharmaceuticals. However, the occurrence of allergic reactions or hypersensitivity and the discovery of PEG antibodies, on the one hand, and the rise of controlled polymerization techniques and novel monomers, on the other hand, have been driving the search for alternative polymers for bioconjugation. The present study describes the synthesis, purification, and properties of conjugates of lysozyme with poly( N-acryloylmorpholine) (PNAM) and poly(oligoethylene glycol methyl ether methacrylate) (POEGMA). Particularly, conjugate species with distinct conjugation degrees are investigated for their residual activity, aggregation behavior, and solubility, by using a high-throughput screening approach. Our study showcases the importance of evaluating conjugates obtained by nonsite-specific modification through isolated species with discrete degrees of conjugation rather than on the batch level. Monovalent conjugates with relatively low molar mass polymers displayed equal or even higher activity than the native protein, while all conjugates showed an improved protein solubility. To achieve a comparable effect on solubility as with PEG, PNAM and POEGMA of higher molar masses were required.

Bulk dynamics of the thermoresponsive random copolymer of di(ethylene glycol) methyl ether methacrylate (MEO2MA) and oligo(ethylene glycol) methyl ether methacrylate (OEGMA)

A thermoresponsive, biocompatible and water soluble copolymer was synthetized via RAFT from 2-(2-methoxyethoxy)ethyl methacrylate (MEO2MA) and oligo (ethylene glycol) methacrylate (OEGMA) in the molar ratio of 9:1.The thermal behavior of the bulk material was investigated through thermogravimetric analysis and differential scanning calorimetry, revealing a fully amorphous polymer whose glass transition's onset is located at -47 °C.The molecular mobility was investigated below and above the glass transition temperature by dielectric relaxation spectroscopy and thermally stimulated depolarization currents, covering the frequency range from 10−3–106 Hz. Multiple relaxation processes were detected. The main process (α) is associated with the dynamical glass transition, whose temperature dependence of relaxation times exhibits the curvature in the relaxation map typical of cooperative processes, with a fragility index characteristic of strong materials. Moreover, two secondary relaxations, β and γ, were observed with Arrhenius temperature dependence of their relaxation times. The β-process show features compatible with a Johari-Goldstein process.Additionally, conductivity of pure dc origin was detected in the low frequency side of the α-relaxation. Its temperature dependence (logσdcvs. 1/T) also shows a curvature indicative of a coupling between charge transport and the segmental relaxation.

Exploring the Long-Term Hydrolytic Behavior of Zwitterionic Polymethacrylates and Polymethacrylamides.

The hydrolytic stability of polymers to be used for coatings in aqueous environments, for example, to confer anti-fouling properties, is crucial. However, long-term exposure studies on such polymers are virtually missing. In this context, we synthesized a set of nine polymers that are typically used for low-fouling coatings, comprising the well-established poly(oligoethylene glycol methylether methacrylate), poly(3-(N-2-methacryloylethyl-N,N-dimethyl) ammoniopropanesulfonate) (“sulfobetaine methacrylate”), and poly(3-(N-3-methacryamidopropyl-N,N-dimethyl)ammoniopropanesulfonate) (“sulfobetaine methacrylamide”) as well as a series of hitherto rarely studied polysulfabetaines, which had been suggested to be particularly hydrolysis-stable. Hydrolysis resistance upon extended storage in aqueous solution is followed by 1H NMR at ambient temperature in various pH regimes. Whereas the monomers suffered slow (in PBS) to very fast hydrolysis (in 1 M NaOH), the polymers, including the polymethacrylates, proved to be highly stable. No degradation of the carboxyl ester or amide was observed after one year in PBS, 1 M HCl, or in sodium carbonate buffer of pH 10. This demonstrates their basic suitability for anti-fouling applications. Poly(sulfobetaine methacrylamide) proved even to be stable for one year in 1 M NaOH without any signs of degradation. The stability is ascribed to a steric shielding effect. The hemisulfate group in the polysulfabetaines, however, was found to be partially labile.

Preparation of well-defined brush-like block copolymers for gene delivery applications under biorelevant reaction conditions.

Well-defined oligo(ethylene glycol) methyl ether methacrylate (OEOMA) based block copolymers with cationic segments composed by N,N-(dimethylamino) ethyl methacrylate (DMAEMA) and/or 2-(diisopropylamino) ethyl methacrylate (DPA) were developed under biorelevant reaction conditions. These brush-type copolymers were synthesized through supplemental activator and reducing agent (SARA) atom transfer radical polymerization (ATRP) using sodium dithionite as SARA agent. The synthesis was carried out using an eco-friendly solvent mixture, very low copper catalyst concentration, and mild reaction conditions. The structure of the block copolymers was characterized by size exclusion chromatography (SEC) analysis and 1H nuclear magnetic resonance (NMR) spectroscopy. The pH-dependent protonation of these copolymers enables the efficient complexation with plasmid DNA (pDNA), yielding polyplexes with sizes ranging from 200 up to 700 nm, depending on the molecular weight of the copolymers, composition and concentration used. Agarose gel electrophoresis confirmed the successful pDNA encapsulation. No cytotoxicity effect was observed, even for N/P ratios higher than 50, for human fibroblasts and cervical cancer cell lines cells. The in vitro cellular uptake experiments demonstrated that the pDNA-loaded block copolymers were efficiently delivered into nucleus of cervical cancer cells. The polymerization approach, the unique structure of the block copolymers and the efficient DNA encapsulation presented can open new avenues for development of efficient tailor made gene delivery systems under biorelevant conditions.

Designing Highly Thermostable Lysozyme–Copolymer Conjugates: Focus on Effect of Polymer Concentration

Designing biomaterials capable of functioning in harsh environments is vital for a range of applications. Using molecular dynamics simulations, we show that conjugating lysozymes with a copolymer [poly(GMA- stat-OEGMA)] comprising glycidyl methacrylate (GMA) and oligo(ethylene glycol) methyl ether methacrylate (OEGMA) results in a dramatic increase of stability of these enzymes at high temperatures provided that the concentration of the copolymer in the close vicinity of the enzyme exceeds a critical value. In our simulations, we use triads containing the same ratio of GMA to OEGMA units as in our recent experiments (N. S. Yadavalli et al., ACS Catalysis, 2017, 7, 8675). We focus on the dynamics of the conjugate at high temperatures and on its structural stability as a function of the copolymer/water content in the vicinity of the enzyme. We show that the dynamics of phase separation in the water-copolymer mixture surrounding the enzyme is critical for the structural stability of the enzyme. Specifically, restricting water access promotes the structural stability of the lysozyme at high temperatures. We identified critical water concentration below which we observe a robust stabilization; the phase separation is no longer observed at this low fraction of water so that the water domains promoting unfolding are no longer formed in the vicinity of the enzyme. This understanding provides a basis for future studies on designing a range of enzyme-copolymer conjugates with improved stability.

PH Responsive Doxorubicin Delivery by Fluorous Polymers for Cancer Treatment.

Polymeric nanoparticles have emerged as valuable drug delivery vehicles as they improve solubility of hydrophobic drugs, enhance circulation lifetime, and can improve the biodistribution profile of small-molecule therapeutics. These nanoparticles can take on a host of polymer architectures including polymersomes, hyperbranched nanoparticles, and dendrimers. We have recently reported that simple low molecular weight fluorous copolymers can self-assemble into nanoparticles and show exceptional passive targeting into multiple tumor models. Given the favorable biodistribution of these particles, we sought to develop systems that enable selective delivery in acidic environments, such as the tumor microenvironment or the lysosomal compartment. In this report, we describe the synthesis and in vitro biological studies of a pH-responsive doxorubicin (DOX) fluorous polymer conjugate. A propargyl DOX hydrazone was synthesized and covalently attached to a water-dispersible fluorous polymer composed of trifluoroethyl methacrylate (TFEMA) and oligo(ethylene glycol) methyl ether methacrylate (OEGMEMA) using the ligand-accelerated copper-catalyzed azide-alkyne cycloaddition. Driven by the high fluorine content of the copolymer carrier, the DOX-copolymer formed stable micelles under aqueous conditions with a hydrodynamic diameter of 250 nm. The DOX-copolymer showed internalization into multiple in vitro models for breast and ovarian cancer. Cytotoxicity assays demonstrated efficacy in both breast and ovarian cancer with overall efficacy being highly dependent on the cell line chosen. Taken together, these results present a platform for the pH-triggered delivery of DOX from a fluorous micelle carrier effective against multiple cancer models in vitro.

A facile method for the controlled polymerization of biocompatible and thermoresponsive oligo(ethylene glycol) methyl ether methacrylate copolymers

Photochemically controlled ATRP-like polymerization is successfully used to prepare a thermoresponsive copolymer of oligo(ethylene glycol) methyl ether methacrylate (OEGMA) and di(ethylene glycol) methyl ether methacrylate (MEO2MA). The photochemically controlled method described here provides good control over the polymer structure, architecture, and properties. This photopolymerization renders polymers with narrow molecular weight distributions (Mw/Mn = 1.3) and high monomer conversions (>90%) while using a very low iridium-based catalyst concentration (25 ppm). In addition, the reaction rate of this polymerization is fast, reaching 50% monomer conversion in less than 1 h of reaction. The lower critical solution temperature (LCST) of the prepared polymer was also adjusted to be in the range of physiological temperatures, undergoing a coil-to-globule transition at 43 °C. In addition, the resulting polymer showed no cytotoxicity on four mammalian cell lines at the highest concentration tested (0.4 mg/ml), which highlights its potential use in different biomedical applications. The thermoresponsive copolymer P(MEO2MA-co-OEGMA500) was successfully prepared using a novel photopolymerization procedure. The synthesis was carried out using a user-friendly method with a few ppm of a photoredox iridium-based catalyst. Monomer conversions higher than 50% were achieved in less than 1 h of synthesis showing a faster polymerization rate when compared to the traditional Cu-based ATRP synthesis. The photochemically controlled method here described provides true control over polymer structure, architecture, and properties. Furthermore, the polymer showed no toxicity on four mammalian cell lines at the highest concentration tested (0.4 mg/ml).

Fabrication of microstructured binary polymer brush "corrals" with integral pH sensing for studies of proton transport in model membrane systems.

Binary brush structures consisting of poly(cysteine methacrylate) (PCysMA) "corrals" enclosed within poly(oligoethylene glycol methyl ether methacrylate) (POEGMA) "walls" are fabricated simply and efficiently using a two-step photochemical process. First, the C-Cl bonds of 4-(chloromethyl)phenylsilane monolayers are selectively converted into carboxylic acid groups by patterned exposure to UV light through a mask and POEGMA is grown from unmodified chlorinated regions by surface-initiated atom-transfer radical polymerisation (ATRP). Incorporation of a ratiometric fluorescent pH indicator, Nile Blue 2-(methacryloyloxy)ethyl carbamate (NBC), into the polymer brushes facilitates assessment of local changes in pH using a confocal laser scanning microscope with spectral resolution capability. Moreover, the dye label acts as a radical spin trap, enabling removal of halogen end-groups from the brushes via in situ dye addition during the polymerisation process. Second, an initiator is attached to the carboxylic acid-functionalised regions formed by UV photolysis in the patterning step, enabling growth of PCysMA brushes by ATRP. Transfer of the system to THF, a poor solvent for PCysMA, causes collapse of the PCysMA brushes. At the interface between the collapsed brush and solvent, selective derivatisation of amine groups is achieved by reaction with excess glutaraldehyde, facilitating attachment of aminobutyl(nitrile triacetic acid) (NTA). The PCysMA brush collapse is reversed on transfer to water, leaving it fully expanded but only functionalized at the brush-water interface. Following complexation of NTA with Ni2+, attachment of histidine-tagged proteorhodopsin and lipid deposition, light-activated transport of protons into the brush structure is demonstrated by measuring the ratiometric response of NBC in the POEGMA walls.

Atomistic insights on the LCST behavior of PMEO2MA in water by molecular dynamics simulations

ABSTRACTFully atomistic molecular dynamics simulations of poly(2‐[2‐methoxyethoxy]ethyl methacrylate) (PMEO2MA) in water at temperatures below and above its lower critical solution temperature (LCST) were performed to improve the understanding of its LCST behavior. Atomic trajectories were used to calculate various structural and dynamic properties. Simulation results show that PMEO2MA undergo a distinct coil‐to‐globule transition above LCST. Detailed analyses of the number of first hydration shell water molecules around various atomic regions are revealed that the water solubility of PMEO2MA below LCST is mainly provided by the hydrophobic hydration around the side chain carbon atoms. This is achieved by the cage‐like water network formations which are disrupted when the temperature is increased above LCST, accompanied by significant amount of water molecule release and local water‐ordering reduction, which leads to the LCST phase transition. Furthermore, other analyses such as the number of hydrogen bonds and hydrogen bond lifetimes suggest that intermolecular hydrogen bondings between polymer and water molecules have little effect on the phase transition. Our results will contribute to a better understanding on the LCST phase transition of oligo(ethylene glycol) methyl ether methacrylate (OEGMA)‐based homopolymers at atomistic level that will be useful when designing homo‐ and co‐polymers of OEGMAs with desired properties. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018, 56, 429–441