Polymethacrylate Backbone Research Articles

Thermoresponsive Brush Coatings for Cell Sheet Engineering with Low Protein Adsorption above the Polymers' Phase Transition Temperature.

Thermoresponsive polymer coatings on cell culture substrates enable noninvasive cell detachment and cell sheet fabrication for biomedical applications. Optimized coatings should support controlled culture and detachment of various cell types and allow chemical modifications, e.g., to introduce specific growth factors for enhanced gene expression. Furthermore, the sterilization and storage stability of the coatings must be assessed for translational attempts. Poly(glycidyl ether) (PGE) brush coatings with short alkoxy side chains provide a versatile platform for cell culture and detachment, but their polyether backbones are susceptible to oxidation and degradation. Thus, we rationally designed potential alternatives with thermoresponsive glycerol-based block copolymers comprising a stable polyacrylate or polymethacrylate backbone and an oligomeric benzophenone (BP)-based anchor. The resulting poly(ethoxy hydroxypropyl acrylate-b-benzophenone acrylate) (pEHPA-b-BP) and poly(ethoxy hydroxypropyl methacrylate-b-benzophenone methacrylate) (pEHPMA-b-BP) block copolymers preserve the short alkoxy-terminated side chains of the PGE derived structure on a stable, but hydrophobic, aliphatic backbone. The amphiphilicity balance is maintained through incorporated hydroxyl groups, which simultaneously can be used for chemical modification. The polymers were tailored into brush coatings on polystyrene surfaces via directed adsorption using the BP oligomer anchor. The resulting coatings with thickness values up to ∼3 nm supported efficient adhesion and proliferation of human fibroblasts despite minimal protein adsorption. The conditions for cell sheet fabrication on pEHPA-b-BP were gentler and more reliable than on pEHPMA-b-BP, which required additional cooling. Hence, the stability of pEHPA-b-BP and PGE coatings was evaluated post gamma and formaldehyde (FO) gas sterilization. Gamma sterilization partially degraded PGE coatings and hindered cell detachment on pEHPA-b-BP. In contrast, FO sterilization only slowed detachment on PGE coatings and had no adverse effects on pEHPA-b-BP, maintaining their efficient performance in cell sheet fabrication.

Covalently Modified Molecular-Recognition-Capable UV-Transparent Microplate for Ultra-High-Throughput Screening of Dissolved Zn2+ and Pb2.

Zn2+ has a crucial role both in biology and the environment, while Pb2+ presents serious hazards in the same areas due to its toxicity, and the need for their analysis often exceeds available instrumental capacity. We report, herein, a new high-throughput optochemical screening method for Zn2+ and Pb2+ in various solutions. Moreover, we also introduced a new and generalizable three-step-microplate-modification technique, including plasma treating, linker-docking and photocatalytic copolymerization. The surface of a commercially available 96-well-cycloolefin-microplate was treated with atmospheric plasma, and then, the bottoms of the wells were covered by covalently attaching a methacrylate-containing linker-monolayer. Finally, the preactivated microplate wells were covalently functionalized by immobilizing bis(acridino)-crown ether-type sensor molecules, via photocatalytic copolymerization, to a polymethacrylate backbone. This sensing tool can be used in all microplate readers, is compatible with liquid handling platforms and provides an unprecedently fast monitoring (>1000 samples/hour, extrapolated from the time required for 96 measurements) of dissolved Zn2+ and Pb2+ among recent alternatives above the detection limits of 8.0 × 10-9 and 3.0 × 10-8 mol/L, respectively, while requiring a sample volume of only 20 µL.

Location of a Hydrophobic Load in Poly(oligo(ethylene glycol) methyl ether methacrylate)s (PEGMAs) Dissolved in Water and Probed by Fluorescence.

Two series of pyrene-labeled poly(oligo(ethylene glycol) methyl ether methacrylate)s referred to as PyEG5-PEGnMA and PyC4-PEGnMA were prepared to probe the region surrounding the polymethacrylate backbone by using the fluorescence of the dye pyrene. PyEG5-PEGnMA and PyC4-PEGnMA were prepared by copolymerizing the EGnMA methacrylate monomers with penta(ethylene glycol) 1-pyrenemethyl ether methacrylate or 1-pyrenebutyl methacrylate, respectively. In organic solvents, the much longer 18 non-hydrogen atom linker connecting the pyrene moieties to the polymethacrylate backbone in the PyEG5-PEGnMA samples enabled the deployment of the pyrenyl labels into the solution. In water, however, an excited pyrene for PyEG5-PEGnMA was found to probe a same volume as for the PyC4-PEGnMA samples where a much shorter 6 non-hydrogen atom spacer connected pyrene to the backbone. Another surprising observation, considering that the hydrophobicity of pyrene induces strong pyrene aggregation for many pyrene-labeled water-soluble polymers (Py-WSPs) in water, was the little pyrene aggregation found for the PyEG5-PEGnMA and PyC4-PEGnMA samples in water. These effects could be related to the organic-like domain (OLD) generated by the oligo(ethylene glycol) side chains densely arranged around the polymethacrylate backbone of the polymeric bottlebrush (PBB). Additional fluorescence experiments conducted with the penta(ethylene glycol) 1-pyrenemethyl ether derivative indicated that the cylindrical OLD surrounding the polymethacrylate backbone had a chemical composition similar to that of ethylene glycol. Binding of hydrophobic pyrene molecules to unlabeled PEGnMA bottlebrushes in water further supported the existence of the OLD. The demonstration, that PEGnMA samples form an OLD in water, which can host and protect hydrophobic cargoes like pyrene, should lead to the development of improved PEGnMA-based drug delivery systems.

Persistence Length and Encounter Frequency Determination from Fluorescence Studies of Pyrene-Labeled Poly(oligo(ethylene glycol) methyl ether methacrylate)s

A series of nine pyrene-labeled poly(oligo(ethylene glycol) methyl ether methacrylate)s (Py-PEGnMAs) with n equal to 0–5, 9, 16, and 19 were prepared by random radical copolymerization of 1-pyrenebutyl methacrylate and nine different EGnMA monomers. The process of pyrene excimer formation (PEF) in the Py-PEGnMA samples was characterized in acetone, THF, toluene, N,N-dimethylformamide (DMF), dioxane, and dimethyl sulfoxide (DMSO). The fluorescence decays of all Py-PEGnMA samples were acquired in the six solvents and analyzed with the fluorescence blob model (FBM) to yield the number Nblob of structural units (SU) in the subvolume of the polymer coil probed by an excited pyrene and referred to as a blob, and the rate constant kblob describing the encounters between two SU bearing an excited and a ground-state pyrenyl label located inside a same blob. Nblob and kblob remained constant with pyrene content for a same series of Py-PEGnMA samples. After averaging Nblob and kblob over all pyrene contents for a same Py-PEGnMA series, ⟨Nblob⟩ and the product ⟨kblob × Nblob⟩ were found to decrease with increasing side chain length reflecting a progressive stiffening and decrease in the internal dynamics of the polymethacrylate backbone, respectively. ⟨Nblob⟩ and ⟨kblob × Nblob⟩ could be parametrized as a function of the molecular weight of an SU and the solvent viscosity. The parametrized form of ⟨Nblob⟩ was applied to determine the persistence length (lp) of the PEGnMA samples using the Kratky–Porod equation. lp was found to increase linearly with the square of the side chain length of the PEGnMA samples, as expected theoretically. The parametrized form of ⟨kblob × Nblob⟩ was used as a calibration curve against which the internal dynamics of several polypeptides and poly(methyl acrylate) could be compared in DMSO. This study illustrates the ability of PEF measurements to determine the persistence length and quantify the internal dynamics of polymers in solution, two important parameters in the characterization of macromolecules.

Characterization of the Local Volume Probed by the Side-Chain Ends of Poly(oligo(ethylene glycol) 1-Pyrenemethyl ether methacrylate) Bottle Brushes in Solution Using Pyrene Excimer Fluorescence

Four poly(oligo(ethylene glycol) 1-pyrenemethyl ether methacrylate) [P(PyEGyMA), with y = 3, 5, 8, and 12] samples were synthesized, where each side chain was terminated with a 1-pyrenemethoxy derivative. The efficiency of excimer formation between an excited-state pyrene and a ground-state pyrene was used to assess the conformation of the PyEGy side chains in these polymeric bottle brushes by conducting time-resolved fluorescence measurements in tetrahydrofuran (THF), N,N-dimethylformamide (DMF), dioxane, and dimethylsulfoxide (DMSO). These experiments took advantage of the dependency of the average rate constant ⟨k⟩ of pyrene excimer formation (PEF) on the local pyrene concentration [Py]loc experienced by an excited pyrene bound to the P(PyEGyMA) samples. [Py]loc could be estimated theoretically by assuming that the EGy side chains adopted a Gaussian conformation. Linear plots of ⟨k⟩/fdiff as a function of [Py]loc, where fdiff is the molar fraction of pyrenyl labels forming excimers by diffusion and was introduced to account for residual pyrene aggregation, were obtained in all four solvents, with slopes that depended on solvent viscosity and the probability of PEF upon the diffusive encounter between two pyrenyl labels. Solvent-induced differences in PEF efficiency could be accounted for by determining the bimolecular rate constant kdiff[inter] for intermolecular PEF with the model compound 1-pyrenemethyl diethylene glycol methyl ether in the four solvents. Except for DMSO, which was too polar and led to the segregation of the pyrenyl labels close to the polymethacrylate backbone, the data obtained for all P(PyEGyMA) samples in THF, DMF, and dioxane collapsed on a master line, similar to the one obtained earlier with a series of pyrene-labeled dendrons, when plotting ⟨k⟩/(fdiff × kdiff[inter])-vs-[Py]loc. The ⟨k⟩/(fdiff × kdiff[inter])-vs-[Py]loc master line confirmed the direct relationship that exists between the PEF efficiency and [Py]loc, a relationship that could be used to probe the conformation of highly branched macromolecules in solution.

All-Polycarbonate Graft Copolymers with Tunable Morphologies by Metal-Free Copolymerization of CO2 with Epoxides

Brush-type macromolecules (BMs) have attracted much attention over the past decades because of their unique properties and potential applications in nanoscience, drug-delivery systems, and photonics. A two-step strategy of synthesis of polycarbonate-grafted copolymers with either star-shaped or brush-typed morphologies using a “grafting from” approach is reported; the backbone in these all-polycarbonate graft copolymers is made of poly(cyclohexene carbonate) (PCHC), and the side grafts are made of poly(propylene carbonate) (PPC). In the first step, poly (vinyl-cyclohexene carbonate) (PVCHC) backbones of two different sizes (PVCHC35, PVCHC283) were prepared by copolymerization of vinyl-cyclohexene oxide (VCHO) with CO2 in the presence of triethylborane (TEB), using tetrabutyl ammonium succinate (TBAS) as the initiator. In the second step, the dangling vinyl double bonds of PVCHC were transformed into carboxylic acid groups. After partial neutralization of the latter using tetrabutyl ammonium hydroxide, the PPC grafts could be grown from the backbone carboxylic sites by copolymerization of propylene oxide (PO) with CO2 in the presence of TEB. Before attempting the synthesis of the above all-polycarbonate grafted copolymers, we check the viability of the above synthetic strategy by preparing graft copolymers made of a polymethacrylate backbone and PPC side grafts. In the latter case, the backbone was generated by reversible addition–fragmentation chain-transfer (RAFT) polymerization of methacrylic acid (MAA), followed by the growth of PPC side grafts using the backbone carboxylates as initiating sites. In both cases (PVCHC-g-PPC and PMAA-g-PPC), two types of architectures corresponding to two different morphologies were synthesized: star-shaped morphologies were obtained from rather short backbones, and relatively long grafts, on the one hand, and semiflexible cylinders were grown from rather long backbones and short grafts. These various structures were characterized by nuclear magnetic resonance (NMR) and gel permeation chromatography/light scattering (GPC/LS), and their morphologies were further investigated by atomic force microscopy (AFM). The reported synthetic method provides a robust way to synthesize well-defined polycarbonates with either star-type or brush-type morphologies and graft copolymers made of polyacrylate backbones and polycarbonate grafts. Thermal and mechanical properties of these graft copolymers were also investigated.

Fluorescent Columnar Liquid‐Crystalline Polymers: Synthesis, Mesomorphic Behaviors and Tunable Emission Wavelengths†

Main observation and conclusionFluorescent columnar liquid‐crystalline polymers have attracted intensive attention due to their unique features that can be applied in many fields. However, the utilization of molecular engineering to achieve efficient fluorescence tuning has rarely been resolved. Herein, we report a series of liquid‐crystalline polymers with α‐cyanostilbene pendants attaching to polymethacrylate backbone by variant length ethylene glycol spacers, that assemble into hexagonal columnar mesophases and exhibit efficient fluorescence emission. Both the columnar ordering and the emission wavelength can be tuned just by altering the length of flexible spacers. With an elongation of the spacer, the columnar ordering and dimensions increased, and the fluorescence emission blue‐shifted gradually. With good correlation of molecular design, columnar structure and fluorescence property, this study is expected to augment the understanding of spacer length influence in liquid‐crystalline polymers and provide a guidance for the design and development of novel functional polymer materials.

PEG Graft Polymer Carriers of Antioxidants: In Vitro Evaluation for Transdermal Delivery.

The in vitro biochemical evaluation of the applicability of polymers carrying active substances (micelles and conjugates) was carried out. Previously designed amphiphilic graft copolymers with retinol or 4-n-butylresorcinol functionalized polymethacrylate backbone and poly(ethylene glycol) (PEG) side chains that included Janus-type heterografted copolymers containing both PEG and poly(ε-caprolactone) (PCL) side chains were applied as micellar carriers. The polymer self-assemblies were convenient to encapsulate arbutin (ARB) as the selected active substances. Moreover, the conjugates of PEG graft copolymers with ferulic acid (FA) or lipoic acid (LA) were also investigated. The permeability of released active substances through a membrane mimicking skin was evaluated by conducting transdermal tests in Franz diffusion cells. The biological response to new carriers with active substances was tested across cell lines, including normal human dermal fibroblasts (NHDF), human epidermal keratinocyte (HaCaT), as well as cancer melanoma (Me45) and metastatic human melanoma (451-Lu), for comparison. These polymer systems were safe and non-cytotoxic at the tested concentrations for healthy skin cell lines according to the MTT test. Cytometric evaluation of cell cycles as well as cell death defined by Annexin-V apoptosis assays and senescence tests showed no significant changes under action of the delivery systems, as compared to the control cells. In vitro tests confirmed the biochemical potential of these antioxidant carriers as beneficial components in cosmetic products, especially applied in the form of masks and eye pads.

Liquid Crystalline Nanowires by Polymerization Induced Hierarchical Self-Assembly

By taking advantage of strong liquid crystallization ordering and photo dimerization of the mesogen stilbene, we propose large-scale synthesis of nanowires of stilbene-containing block copolymers by polymerization induced hierarchical self-assembly. The interior of nanowires is in the type of liquid crystal (LC) structure with highly ordered smectic LC layers, which are perpendicular to the long axis. The alternative striped structure consists of the polymethacrylate backbone and stilbene-containing side chain. The approach is general toward stilbene-containing block copolymer LC nanowires, irrelevant with the composition of stabilizer blocks. The nanowires become robust with the layered structure preserved after cross-linking via dimerization upon UV irradiation. The nanowires reported here may provide one-dimensional model blocks toward superstructures, which can be used in the fields of electric nanoconductors, functional additives, etc.

Efficient synthesis of a rod-coil conjugated graft copolymer by combination of thiol-maleimide chemistry and MOF-catalyzed photopolymerization

While several strategies have been developed in the literature to obtain rod-coil graft copolymers composed of regioregular poly(3-hexyl thiophene) (P3HT), our contribution in this field consists of a convenient and versatile way to obtain a copolymer with a coil polymethacrylate backbone grafted with P3HT rod chains by a combination of the thiol-maleimide chemistry and MOF-catalyzed photoinitiated atom transfer radical polymerization (ATRP) method. Well-defined synthesis of the P3HT-graft copolymer was described, and its structure, morphology and properties were characterized by proton nuclear magnetic resonance, gel permeation chromatography, Fourier transform infrared, UV–vis and photoluminescence spectroscopy, differential scanning calorimetry and atomic force microscopy.

Suitability of ethyl cellulose as multifunctional additive for blends of vegetable oil-based lubricants

In a previous study, ethyl cellulose was successfully blended with castor oil and the results demonstrated its suitability to be used as additive to expand the range of operating conditions under which fluid film lubrication is sustained, mainly at high temperature. However, apparent solubility problems were detected when mixed with other vegetable oils with lower polarity than castor oil. In this work, a suitable combination of ethyl cellulose (EC) with both high oleic sunflower (HOSO) and castor (CO) oils was found able to reach stable and non gel-like blends with viscosities at 40 °C ranging between 62 and 493 cSt, and viscosity indexes fitting into group III (VI ≥ 120) of API classification of base fluids. The ternary HOSO/CO/EC blend showed an important reduction in friction coefficient at low entrainment speed, and generated a stable EHD-film at 100 °C of around 20 nm, which suggests better boundary properties than HOSO/EC or CO/EC blends. On the other hand, ethyl cellulose hindered wax crystallization process of these vegetable oil-based lubricants at 5 °C, yielding comparable results to those obtained with standard polymethacrylate backbone additives. Therefore, the suitable combination of both castor and HOSO with EC as multifunctional additive allow a set of eco-friendly base fluids to be formulated with a wide kinematic viscosity range, better viscosity-temperature dependence than many mineral or synthetic oils lubricants and excellent boundary lubrication properties, making them suitable for many lubricant applications.

Produce Molecular Brushes with Ultrahigh Grafting Density Using Accelerated CuAAC Grafting-Onto Strategy

A method was developed to synthesize molecular brushes with polymethacrylate backbone and ultrahigh density of grafted side chains (SCs), i.e., 1.34 SCs per backbone carbon atom, using accelerated copper-catalyzed azide–alkyne cycloaddition (CuAAC) grafting-onto strategy. This acceleration effect that benefits from the complexation of triazole with Cu was first confirmed in two model CuAAC reactions of (a) 1:1 molar ratio of a diazide compound and an alkynyl-terminated poly(ethylene oxide) (ay-PEO18 with average degree of polymerization DP = 18) and (b) 1:1 molar ratio of a dialkyne compound and an azido-terminated N3-PEO18. It was found that both model reactions produced ditriazoles as major products, although the former reaction exhibited a higher yield of PEO–PEO dimers, demonstrating better CuAAC acceleration effect. Following this principle, polymethacrylate backbones with multiazido dangling groups were subsequently used for grafting-onto reaction with ay-SCs to prepare an array of molecular brushes...

Influence of main chain on the phase behaviors of side‐chain liquid‐crystalline polymers with triphenylene mesogens of long alkyl tail substituents

ABSTRACTA series of side‐chain liquid‐crystalline polymers (SCLCPs) containing triphenylene mesogen, in which the long alkyl tail Tp connected directly with main chain, were synthesized successfully. The chemical structures of the monomers were confirmed by 1H NMR and mass spectrometry. The phase behaviors of polymers were investigated by a combination of techniques, including DSC, POM, 1D/2D WAXD, and SAXS. The experimental results suggested that the type of main chain played an important role in the LC phase structures of these polymers. Because of the steric effects of side chains and the coupling effects between the Tp moieties and the main chains, all the polymers exhibited columnar phase. However, the SCLCPs with poly(vinyl benzene methyl ether) or polynorbornene backbone displayed hexagonal columnar phase, while those with polyacrylate or polymethacrylate backbone presented columnar nematic phase, and the one with poly(vinyl benzoate) main chain showed rectangular columnar phase. Moreover, the clearing temperatures (Ti) changed with change in main chain. Especially, the Ti of the SCLCP with polymethacrylate backbone was above 300 °C. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 754–766

Preparation of titania nanoparticles with tunable anisotropy and branched structures from core–shell molecular bottlebrushes

Abstract Core–shell molecular bottlebrushes with various topologies and with poly (tert-butyl acrylate)-b-polystyrene (PtBA-b-PS) block copolymer side chains were synthesized via atom transfer radical polymerization (ATRP). After hydrolysis of the PtBA segments and their conversion to poly (acrylic acid) (PAA), the materials were used as templates to prepare titania nanoparticles. Transmission electron microscopy (TEM) images showed that the particles retained the characteristic shape of the templates, including branches and cylindrical geometry. The cylindrical dimensions, i.e. diameter and length, were controlled by the number average degrees of polymerization of the PAA side-chain block and the polymethacrylate backbone, respectively. Thermogravimetric analysis (TGA) showed the weight fraction of inorganic content ranged from 17% to 35%, depending on the ratio of the length of PAA and PS blocks.

Trehalose glycopolymer hydrogels and conjugates for protein stabilization

Event Abstract Back to Event Trehalose glycopolymer hydrogels and conjugates for protein stabilization Heather Maynard1 1 UCLA, Chemistry and Biochemistry, United States Introduction: Therapeutic proteins are challenging to transport and store and the majority need to be refrigerated or frozen. Proteins exposed to these stressors often lose activity. This can be harmful or even fatal for patients that take the medicines. Thus polymers and hydrogels that are capable of stabilizing biomolecules at room temperature are of significant interest. The disaccharide sugar, trehalose, is known to stabilize proteins to a variety of environments including to elevated temperatures and desiccation. We hypothesized that by preparing polymers with side chain trehalose units, the resulting materials would also stabilize proteins. This talk will focus on linear polymer conjugates and hydrogels with trehalose as a component for protein stabilization. Results and Discussion: A library of polymers with polystyrene or polymethacrylate backbones and trehalose side chains was prepared by free radical polymerization. Therapeutic proteins such as insulin were tested under stress conditions such as heat with and without added polymer. The polymers that performed optimally in this exercise were utilized to prepare conjugates with the therapeutic proteins. This was accomplished by synthesizing the polymers by reversible addition-fragmentation chain transfer (RAFT) polymerization utilizing functional chain transfer agents (CTA) so that the resulting polymers contained end groups reactive to amino acid side chains on proteins. The polymers were then conjugated to the proteins and the resulting conjugates purified by fast protein liquid chromatography. Pharmacokinetics in mice, in vitro and in vivo bioactivity, and stability to elevated temperatures were evaluated. The results showed that the trehalose polymers were able to (a) enhance the plasma half life similar to gold standard poly(ethylene glycol) (PEG), (b) remain bioactive similar to the analogous PEGylated proteins, and (c) stabilize the proteins to elevated temperatures. They were also non-toxic in vitro and in vivo. Discussion of this research will encompass the first part of the talk. Hydrogels were also prepared by either free radical polymerization of the trehalose monomers and trehalose crosslinkers or by specific condensation reactions between the trehalose polymers and boronic acid end-functionalized PEGs. Both cases resulted in gels that could incorporate and stabilize proteins such as insulin to thermal stress. The gels released the proteins by passive release or by triggered release by glucose, respectively. This research will be discussed in the second part of this talk. Conclusions: Trehalose materials, also called PolyProtek, are excellent protein stabilizers. Make in a linear form, the polymers form therapeutic protein conjugates that are bioactive and stable to temperatures and in vivo. As a hydrogel the materials can stabilize prior to triggered release of proteins. Thus, trehalose materials are promising for therapeutic applications. National Science Foundation (grants CHE-1112550 and CHE-1507735) Keywords: Hydrogel, Drug delivery, Bioactivity, Polymeric material Conference: 10th World Biomaterials Congress, Montréal, Canada, 17 May - 22 May, 2016. Presentation Type: New Frontier Oral Topic: Nano-structured materials for unique functions Citation: Maynard H (2016). Trehalose glycopolymer hydrogels and conjugates for protein stabilization. Front. Bioeng. Biotechnol. Conference Abstract: 10th World Biomaterials Congress. doi: 10.3389/conf.FBIOE.2016.01.01532 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 27 Mar 2016; Published Online: 30 Mar 2016. Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Heather Maynard Google Heather Maynard Google Scholar Heather Maynard PubMed Heather Maynard Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Effect of Polyethylene Glycol Immobilized into a Polymethacrylate Matrix on the Sorption of Rhodamine

Combined matrix PMMA and PEG, having a polymethacrylate backbone and hydrophilic PEG chains, has been synthesized and applied for the design of transparent colour sensors. Introduction of the hydrophilic PEG chains in the PMMA bulk overcomes the limitations caused by the hydrophobicity of PMMA, and exhibits good wettability, stable and specific adsorption. We suppose that the adsorption of rhodamine on such networks depends on the chemical composition of the system and describes the interaction of the xanthene dye with the polymers.

Poly(ethylenimine)-Based Polymer Blends as Single-Ion Lithium Conductors

Highly conductive solid polymer electrolytes were generated by blending linear poly(ethyleneimine)-graft-poly(ethylene glycol) with linear poly(ethyleneimine) bearing lithium N-propylsulfonate groups as the lithium source. The effect of polymer backbone structure on Li+ conductivity was determined by comparing a series of blends made from the PEI-based materials with those from polymethacrylate backbone analogues. The use of PEI backbones promoted ion-pair dissociation, stabilized the macromolecular mix and generated blends with ionic conductivities up to 2 orders of magnitude higher than those of the polymethacrylate-based systems. Blends containing the PEI-bound lithium sulfonates exhibited lithium conductivities higher than those measured for PEG doped with lithium bis(trifluoromethyl)sulfonimide. Shifts in the νs(SO3) IR absorption band suggest that the solvation environment for the lithium sulfonates changes with polymer structure. The PEI-based blends are thermally stable up to 200 °C, electrochemic...

Synthesis and properties of a dually cleavable graft copolymer comprising pendant acetal linkages

A novel disulfide- and acetal-linked graft copolymer (SACG) comprising acetal-bridged poly(e-caprolactone)-b-poly(ethylene glycol) and PEG pendent chains and relatively short polymethacrylate backbone (DP ≈ 24) was synthesized and self-assembled for in vitro encapsulation and release of an anticancer drug, doxorubicin (DOX). Three-step reactions involving (i) RAFT copolymerization of 2-hydroxyethyl methacrylate and poly(ethylene glycol) methyl ether methacrylate, (ii) ring-opening polymerization to generate PCL chains, and (iii) hydroxyl-vinyloxy adductive reaction to introduce acid-cleavable PEG segments were used to achieve the target copolymer. Meanwhile, well-defined normal (CP) and disulfide-linked (SCP) poly(PEG-co-PCL) comb-like copolymers and acid-cleavable poly(PEG-co-PCL)-graft-MVPEG copolymer (ACG) were synthesized and acted as analogues of SACG upon external stimuli. The macromolecular architecture significantly affected the melting and crystallization behaviors and aggregation properties of copolymers, and the difference in topology and location of cleavable linkages resulted in distinctly different stimuli-triggered drug release behaviors. Owing to the dissociation and reaggregation of cleaved copolymer aggregates, stimuli-cleavable aggregates in response to external stimuli (pH 5.0, 10 mM DTT) could exhibit faster release kinetics than CP aggregates, and the maximum increment of cumulative release from various aggregates for 72 h was liable to decrease in the order SACG > ACG > SCP > CP. The cumulative release from SACG aggregates could be adjusted in the widest range via addition of different stimuli, revealing the great potential of dually cleavable copolymer aggregates in smart drug delivery systems.

Modeling mechanophore activation within a viscous rubbery network

Mechanically induced chemical reactivity is a promising means for designing self-sensing and autonomous materials. Force sensitive chemical groups called mechanophores can be covalently linked into polymers in order to trigger specific chemical reactions upon mechanical loading. A model framework is developed to describe the response of these mechanophores to mechanical loading within an elastomeric matrix. A multiscale modeling scheme is used to couple mechanophore kinetics with rubbery elasticity. In particular, transition state theory for the population of mechanophores is modified to account for the stress-induced changes in kinetics within the solid state. The model is specified to the case of spiropyran covalently linked into a polymethacrylate (PMA) backbone. This optically trackable mechanophore (optically active through absorption and fluorescence when triggered) allows the model to be assessed in comparison to observed experimental behavior. The activation predicted by the ideal viscous elastomer model is reasonable, but consistently occurs at a larger strain than in the experiments. The glassy portion of the PMA response accounts for part of the difference in the onset of activation between experiments and the ideal elastomer model. The glassy stress response is therefore included as an additional empirically determined driving force for activation in the model. The remainder of the discrepancy between the experimental and simulation results is attributed to force inhomogeneity within the rubbery network, highlighting that the mechanophore response is correlated with local force history rather than with macroscopic stress.

Easy Access to Amphiphilic Heterografted Poly(2-oxazoline) Comb Copolymers

A series of heterografted polymers with a polymethacrylate backbone and varying composition of oligomeric 2-oxazoline side chains was synthesized by copolymerization of oligo(2-ethyl-2-oxazoline)me...