Polymer Pendant Research Articles

Synthesis and Controlled Cargo Release of Novel Photoresponsive Polysiloxane‐Based Single‐Chain Nanoparticles

AbstractHerein, a novel, highly branched and photoresponsive polysiloxane is synthesized and studied. The polymer is photoconstructed into a single‐chain nanoparticle loaded with Nile Red and Metformin. Through the photoreversible [2+2] mechanism of the polymer's pendant coumarin moieties, the nanoparticles are de‐crosslinked, and their cargo molecules released. A study of the kinetics of release is undertaken in different solvents, providing insight into the relationship between the cargo's molecular structure and that of the polymer chain. On the whole, this report's study introduces new controlled release and cationic ring‐opening polymerization concepts while providing the first example of a single‐chain polymer nanoparticle based on a photoresponsive polysiloxane.

A Remarkable Impact of pH on the Thermo-Responsive Properties of Alginate-Based Composite Hydrogels Incorporating P2VP-PEO Micellar Nanoparticles.

A heterograft copolymer with an alginate backbone, hetero-grafted by polymer pendant chains displaying different lower critical solution temperatures (LCSTs), combined with a pH-responsive poly(2-vinyl pyridine)-b-poly(ethylene oxide) (P2VP-b-PEO) diblock copolymer forming micellar nanoparticles, was investigated in aqueous media at various pHs. Due to its thermo-responsive side chains, the copolymer forms hydrogels with a thermo-induced sol-gel transition, above a critical temperature, Tgel (thermo-thickening). However, by lowering the pH of the medium in an acidic regime, a remarkable increase in the elasticity of the formulation was observed. This effect was more pronounced in low temperatures (below Tgel), suggesting secondary physical crosslinking, which induces significant changes in the hydrogel thermo-responsiveness, transforming the sol-gel transition to soft gel-strong gel. Moreover, the onset of thermo-thickening shifted to lower temperatures followed by the broadening of the transition zone, implying intermolecular interactions between the uncharged alginate backbone with the PNIPAM side chains, likely through H-bonding. The shear-thinning behavior of the soft gel in low temperatures provides injectability, which allows potential applications for 3D printing. Furthermore, the heterograft copolymer/nanoparticles composite hydrogel, encapsulating a model hydrophobic drug in the hydrophobic cores of the nanoparticles, was evaluated as a pH-responsive drug delivery system. The presented tunable drug delivery system might be useful for biomedical potential applications.

Main-chain side-chain combined liquid crystalline polymers bearing azobenzene and biphenyl-based mesogens – segregation of the mesogens within two distinct layers

ABSTRACT Two different mesogenic units, namely biphenyl and azobenzene, were installed centrally within the polymer backbone and pendant alkylene segments; the purpose was to examine if chain folding of the backbone occurs so as to segregate the azobenzene and biphenyl units in adjacent layers of a smectic-type ordering. Two sets of isomeric main-chain side-chain liquid crystalline polymers (MCSC-LCPs), namely SC-AzoCx-MC-BPCx and SC-BPCx-MC-AzoCx (x=6 or 10), were synthesised; the former series has biphenyl in the backbone and azobenzene in the side-chain, while their locations are switched in the latter. It was observed that all four polymers were semicrystalline at room temperature and exhibited a smectic mesophase upon melting. DSC and X-ray scattering studies revealed that switching the locations of the azobenzene and biphenyls had little effect on; the phase transition temperatures and smectic layer spacings. A second series, namely SC-AzoCx-MC-BPCy and SC-BPCx-MC-AzoCy, where the length of alkylene spacers in the side-chain (Cx) and backbone (Cy) is different, was also studied; this was done to examine the influence of unequal alkylene segment lengths on the mesophase structure and interlayer spacing, and importantly, whether the zigzag folding-induced formation of a layered structure is retained, despite their unsymmetrical nature.

Responsive Polyesters with Alkene and Carboxylic Acid Side-Groups for Tissue Engineering Applications.

Main chain polyesters have been extensively used in the biomedical field. Despite their many advantages, including biocompatibility, biodegradability, and others, these materials are rather inert and lack specific functionalities which will endow them with additional biological and responsive properties. In this work, novel pH-responsive main chain polyesters have been prepared by a conventional condensation polymerization of a vinyl functionalized diol with a diacid chloride, followed by a photo-induced thiol-ene click reaction to attach functional carboxylic acid side-groups along the polymer chains. Two different mercaptocarboxylic acids were employed, allowing to vary the alkyl chain length of the polymer pendant groups. Moreover, the degree of modification, and as a result, the carboxylic acid content of the polymers, was easily tuned by varying the irradiation time during the click reaction. Both these parameters, were shown to strongly influence the responsive behavior of the polyesters, which presented adjustable pKα values and water solubilities. Finally, the difunctional polyesters bearing the alkene and carboxylic acid functionalities enabled the preparation of cross-linked polyester films by chemically linking the pendant vinyl bonds on the polymer side groups. The biocompatibility of the cross-linked polymers films was assessed in L929 fibroblast cultures and showed that the cell viability, proliferation, and attachment were greatly promoted on the polyester surface, bearing the shorter alkyl chain length side groups and the higher fraction of carboxylic acid functionalities.

Preparation of bottlebrush polymer-modified magnetic graphene as immobilized metal ion affinity adsorbent for purification of hemoglobin from blood samples.

An immobilized metal affinity (IMA) adsorbent was prepared by grafting bottlebrush polymer pendant with iminodiacetic acid (IDA) from the surface of polydopamine (PDA)-coated magnetic graphene oxide (magGO), via surface-initiated atom transfer radical polymerization (SI-ATRP). Poly(hydroxyethyl methacrylate) (PHEMA) was grafted firstly from the PDA-coated magGO as the backbone, and then poly(glycidyl methacrylate) was grafted from the PHEMA chains via the second SI-ATRP to afford the bottlebrush polymer-grafted magGO Thereafter,IDA was anchored on the nanocomposites to produce the IMA adsorbent after chelating copper ions. The adsorbent was characterized by various physical and physicochemical methods. Its adsorption properties were evaluated by using histidine-rich proteins (bovine hemoglobin, BHb) and other proteins (lysozyme and cytochrome-C). The results show that its maximum adsorption capacity to BHb was 378.6mgg-1, and the adsorption equilibrium can be quickly reached within 1h. The adsorbent has excellent reproducibility and reusability. It has beenapplied to selectively purify hemoglobin from human whole blood, indicating its potential in practical applications. Graphical abstract.

Polymers for dye transfer inhibition in laundry applications

AbstractThe deposition of dyes onto lightly colored garments, or onto lighter sections of multicolored garments, during laundry results in fabric discoloration. In particular, there is a requirement to restrict indigo dye transfer between garments. Polymers may be added to detergent formulations as dye transfer inhibitors to prevent dye transfer by blocking the deposition of fugitive dyes in aqueous solution. This article reports the generation of a range of dye transfer inhibitors produced by condensation reactions that are effective in preventing the transfer of unbound indigo dye to a variety of fiber types. Key design rules relating to polymer hydrophilicity and pendant polymer functionality were established for the creation of effective dye transfer inhibitors. Remarkably, polymers at concentrations as low as 0.1 mg/ml were found to be effective in inhibiting indigo deposition on a variety of fiber types, offering great promise for their inclusion within laundry detergent formulations as dye transfer inhibitors.

An overview of synthetic modification of nitrile group in polymers and applications

AbstractThe physicochemical properties of polymers are mainly dependent on the nature of polymer backbone and/or pendant groups linked to the main chain. Therefore, synthetic modification of these functional groups via post functionalization is an important approach for obtaining novel polymeric systems with improved properties and targeted applications. In this context, the synthetic modifications of nitrile group in polymers into various useful functionalities have received considerable attention and several interesting applications of the resulting polymers have been identified. The majority of the studies are based on Polyacrylonitrile (PAN), and some isolated examples of nitrile functionalization in copolymers such as Poly (Styrene‐co‐Acrylonitrile) (SAN), Poly (Acrylonitrile‐co‐Butadiene‐co‐Styrene (ABS) and Nitrile Rubber (NBR) are available. These synthetic modifications are mainly accomplished by the reactions such as Nucleophilic addition, cycloaddition, reduction, and hydrolysis using various reagents. These studies describing the post‐polymerization modifications of nitrile group in polymers reported during the last three decades are covered in this review.

All-Organic Semiconductors for Electrochemical Biosensors: An Overview of Recent Progress in Material Design.

Organic semiconductors remain of major interest in the field of bioelectrochemistry for their versatility in chemical and electrochemical behavior. These materials have been tailored using organic synthesis for use in cell stimulation, sustainable energy production, and in biosensors. Recent progress in the field of fully organic semiconductor biosensors is outlined in this review, with a particular emphasis on the synthetic tailoring of these semiconductors for their intended application. Biosensors ultimately function on the basis of a physical, optical or electrochemical change which occurs in the active material when it encounters the target analyte. Electrochemical biosensors are becoming increasingly popular among organic semiconductor biosensors, owing to their good detection performances, and simple operation. The analyte either interacts directly with the semiconductor material in a redox process or undergoes a redox process with a moiety such as an enzyme attached to the semiconductor material. The electrochemical signal is then transduced through the semiconductor material. The most recent examples of organic semiconductor biosensors are discussed here with reference to the material design of polymers with semiconducting backbones, specifically conjugated polymers, and polymer semiconducting dyes. We conclude that direct interaction between the analyte and the semiconducting material is generally more sensitive and cost effective, despite being currently limited by the need to identify, and synthesize selective sensing functionalities. It is also worth noting the potential roles of highly-sensitive, organic transistor devices and small molecule semiconductors, such as the photochromic and redox active molecule spiropyran, as polymer pendant groups in future biosensor designs.

Influence of side-chain length on long-term release kinetics from poly(2-oxazoline)-drug conjugate networks

Four drug-conjugated poly(2-alkyl-2-oxazoline) (PAOx) networks with different hydrophobicity were synthesized via copolymerization of either 2-methyl-, 2-ethyl-, 2-propyl- or 2-butyl-2-oxazoline with the functional monomer, 2-dec-9-enyl-2-oxazoline. The incorporation of a labile ester linkage between the polymer and the drug benazepril allowed for sustained drug release over periods of months with the release rates strongly depending on the hydrophobicity of the polymer pendant groups. Drug loading of 13 ± 2 wt% was used with 10 mol% crosslinking sites simply by tuning the thiol-ene stoichiometry. The networks exhibited negligible cell toxicity but cell repulsion was observed for hydrogels based on poly(2-methyl-2-oxazoline) and poly(2-ethyl-2-oxazoline) while those based on poly(2-n-propyl-2-oxazoline) and poly(2-n-butyl-2-oxaoline) showed cell adhesion. These results suggest that PAOx networks have great potential as drug delivery devices for long-lasting drug release applications.

High-Throughput Assessment and Modeling of a Polymer Library Regulating Human Dental Pulp-Derived Stem Cell Behavior.

The identification of biomaterials that modulate cell responses is a crucial task for tissue engineering and cell therapy. The identification of novel materials is complicated by the immense number of synthesizable polymers and the time required for testing each material experimentally. In the current study, polymeric biomaterial-cell interactions were assessed rapidly using a microarray format. The attachment, proliferation, and differentiation of human dental pulp stem cells (hDPSCs) were investigated on 141 homopolymers and 400 diverse copolymers. The copolymer of isooctyl acrylate and 2-(methacryloyloxy)ethyl acetoacetate achieved the highest attachment and proliferation of hDPSC, whereas high cell attachment and differentiation of hDPSC were observed on the copolymer of isooctyl acrylate and trimethylolpropane ethoxylate triacrylate. Computational models were generated, relating polymer properties to cellular responses. These models could accurately predict cell behavior for up to 95% of materials within a test set. The models identified several functional groups as being important for supporting specific cell responses. In particular, oxygen-containing chemical moieties, including fragments from the acrylate/acrylamide backbone of the polymers, promoted cell attachment. Small hydrocarbon fragments originating from polymer pendant groups promoted cell proliferation and differentiation. These computational models constitute a key tool to direct the discovery of novel materials within the enormous chemical space available to researchers.

Synthesis, self-assembly, and pH-responsive drug release of PHMEMA-PEG-PHMEMA ABA triblock copolymers

A series of tertiary amine containing PHMEMA-PEG-PHMEMA ABA triblock copolymers were synthesized by atom transfer radical polymerization (ATRP) using bromine-capped poly(ethylene glycol) (Br-PEG-Br) and 2-(hexamethyleneimino)ethyl methacrylate (HMEMA) as macro-initiator and monomers, respectively. The chemical structures and molecular weights of triblock copolymers were characterized by 1H NMR and gel permeation chromatography (GPC). The self-assembly behaviors of copolymers in different pH conditions were studied by dynamic light scattering (DLS) and transmission electron microscopy (TEM). Triblock copolymers self-assembled into micelles in water (pH 7.4) and the micelles disassembled at acidic pH (pH 5.0). Anticancer drug doxorubicin (DOX) was used as a drug model and physically encapsulated into polymeric micelles. The drug release of DOX-loaded polymeric micelles was pH-responsive; the drug-loaded micelles that had higher contents of tertiary amine in polymer pendant groups showed faster release speed. In addition, the drug-loaded micelles showed excellent inhibition efficacy against HeLa cells in vitro.

The synthesis and self-assembly of bioconjugates composed of thermally-responsive polymer chains and pendant lysozyme molecules

Thermal-responsive polymer chains with pendant lysozyme molecules were prepared via a “grafting to” approach. The bioconjugates were able to self-assemble into mesoglobules at a temperature above their cloud point.

Drug-free macromolecular therapeutics: Impact of structure on induction of apoptosis in Raji B cells

Recently, we developed a new paradigm in macromolecular therapeutics that avoids the use of low molecular weight drugs. The activity of the “drug-free macromolecular therapeutics” is based on the biorecognition of complementary motifs at cell surface resulting in receptor crosslinking and apoptosis induction. The system is composed of two nanoconjugates: (1) a single-stranded morpholino oligonucleotide (MORF1) attached to an anti-CD20 Fab′ fragment (Fab′-MORF1); (2) multiple copies of complementary oligonucleotide MORF2 grafted to a linear polymer of N-(2-hydroxypropyl)methacrylamide (HPMA) – P-(MORF2)x. The two conjugates crosslink CD20 antigens via MORF1-MORF2 hybridization at the surface of CD20+ malignant B-cells and induce apoptosis. Preclinical studies in a murine model of human non-Hodgkin's lymphoma showed cancer cells eradication and long-term survivors. The aim of this study was to determine the relationship between the detailed structure of the nanoconjugates and apoptosis induction in Raji cells to allow system optimization. The factors studied include the length of the MORF sequence, the valence of P-(MORF2)x (varying x), molecular weight of P-(MORF2)x, incorporation of a miniPEG spacer between Fab′ and MORF1 and between polymer backbone and pendant MORF2, and comparison of two Fab′ fragments, one from 1F5 antibody (Fab′1F5), the other from Rituximab (Fab′RTX). The results of apoptosis induction in human Burkitt's B-cell non-Hodgkin's lymphoma (NHL) Raji cells as determined using three apoptotic assays (Annexin V, Caspase 3, and TUNEL) indicated that: a) An improvement of apoptotic activity was observed for a 28 base pair MORF sequence when compared to MORFs composed of 20 and 25 base pairs. The differences depended on type of assay, concentration and exposure schedule (consecutive vs. premixed). b) The higher the valence of P-(MORF2)x the higher the levels of apoptosis. c) Higher molecular weight of P-(MORF2)x induced higher levels of apoptosis. d) A miniPEG8 spacer was effective in enhancing apoptotic levels in contrast to a miniPEG2 spacer. e) There was not a statistically significant difference when comparing Fab′1F5-MORF1 with Fab′RTX-MORF1.

Recent advances in the syntheses of radical-containing macromolecules

Tailor-made polymers containing specific chemical functionalities have ushered in a number of emerging fields in polymer science. In most of these next-generation applications the focus of the community has centered upon closed-shell macromolecules. Conversely, macromolecules containing stable radical sites have been less studied despite the promise of this evolving class of polymers. In particular, radical-containing macromolecules have shown great potential in magnetic, energy storage, and biomedical applications. Here, the progress regarding the syntheses of open-shell containing polymers are reviewed in two distinct subclasses. In the first, the syntheses of radical polymers (i.e., materials composed of non-conjugated macromolecular backbones and with open-shell units present on the polymer pendant sites) are described. In the second, polyradical (i.e., macromolecules containing stabilized radical sites either within the macromolecular backbone or those containing radical sites that are stabilized through a large degree of conjugation) synthetic schemes are presented. Thus, the state-of-the-art in open-shell macromolecular syntheses will be reported and future means by which to advance the current archetype will be discussed. By detailing the synthetic pathways possible for, and the inherent synthetic limitations of, the creation of these functional polymers, the community will be able to extend the bounds of the radical-containing macromolecular paradigm. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 1875–1894

ToF-SIMS analysis of a polymer microarray composed of poly(meth)acrylates with C6 derivative pendant groups.

Surface analysis plays a key role in understanding the function of materials, particularly in biological environments. Time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) provides highly surface sensitive chemical information that can readily be acquired over large areas and has, thus, become an important surface analysis tool. However, the information‐rich nature of ToF‐SIMS complicates the interpretation and comparison of spectra, particularly in cases where multicomponent samples are being assessed. In this study, a method is presented to assess the chemical variance across 16 poly(meth)acrylates. Materials are selected to contain C6 pendant groups, and ten replicates of each are printed as a polymer microarray. SIMS spectra are acquired for each material with the most intense and unique ions assessed for each material to identify the predominant and distinctive fragmentation pathways within the materials studied. Differentiating acrylate/methacrylate pairs is readily achieved using secondary ions derived from both the polymer backbone and pendant groups. Principal component analysis (PCA) is performed on the SIMS spectra of the 16 polymers, whereby the resulting principal components are able to distinguish phenyl from benzyl groups, mono‐functional from multi‐functional monomers and acrylates from methacrylates. The principal components are applied to copolymer series to assess the predictive capabilities of the PCA. Beyond being able to predict the copolymer ratio, in some cases, the SIMS analysis is able to provide insight into the molecular sequence of a copolymer. The insight gained in this study will be beneficial for developing structure–function relationships based upon ToF‐SIMS data of polymer libraries. © 2016 The Authors Surface and Interface Analysis Published by John Wiley & Sons Ltd.

Formation of nanometer-thick delaminated amorphous carbon layer by two-step plasma processing of methacrylate-based polymer

The authors show that extended He plasma pretreatment (PPT) of methacrylate-based 193 nm photoresist (PR) material in conjunction with a subsequent biased Ar plasma treatment can lead to blister formation at the polymer surface due to delamination of an ultrathin, ion-induced, dense, amorphous carbon (DAC) layer formed by low energy ion bombardment. For our experimental conditions, the delaminated layer is 1–2 nm thick and primarily composed of sp2-hybrized amorphous carbon. A He or Ar plasma process alone will not lead to this phenomenon, and so far the authors have only observed it for a methacrylate polymer. A possible mechanism of the formation of the ultrathin layer that is consistent with all observations is as follows: During He plasma pretreatment, volatile species are produced by ultraviolet/vacuum ultraviolet radiation-induced photolysis of the polymer pendant groups, e.g., adamantyl and chain-scissioning of the polymer backbone to a depth of greater than 100 nm. While volatile products formed close to the polymer surface can diffuse out during He PPT, those formed deep within the polymer bulk cannot and their concentration will become significant for extended He PPT. During the biased Ar plasma treatment step, a DAC surface layer is generated by Ar+ ion bombardment within the first seconds of plasma exposure. The thickness is dependent on ion energy and in the range of one to several nanometers. This layer appears to be impermeable to gaseous products formed in the PR material. Thus, volatile species diffusing to the surface can accumulate underneath the DAC layer, causing a loss of adhesion and subsequent delamination of this layer from the PR bulk film. The authors also report surface and electrical characterizations of the ultrathin DAC layer using optical microscopy, transmission electron microscopy, Raman and x-ray photoemission spectroscopy, and two-point probe techniques.

Cross-linked poly(arylene ether ketone) proton exchange membranes sulfonated on polymer backbone, pendant, and cross-linked sites for enhanced proton conductivity

The sulfonated poly(arylene ether ketone) (SPAEK) precursor containing pendant carboxylic groups was synthesized, and used for the production of a series of cross-linked sulfonated poly(arylene ether ketone) membranes with different cross-linking density, using the carboxylic acid reactive groups. In order to obtain high proton conductivity, the sulfonated groups were attached not only on the polymer backbone, but also on the pendant and cross-linked sites. The chemical synthesis of SPAEK was confirmed using 1H-NMR and FT-IR spectroscopy. The proton conductivity, water uptake, mechanical properties, and morphology of the cross-linked membranes (CSPAEK) prepared were investigated, and correlated with the ionic cluster dimension. The use of sulfonated cross-linker had an excellent effect on the overall membrane properties. It enhanced the mechanical properties but noticeably lowered the water uptake, while still maintaining proton conductivity at a high level. Even the CSPAEK membrane with 15% cross-linking degree exhibited higher proton conductivity than Nafion® 117, while demonstrating acceptable water uptake and tensile strength. The ion cluster dimension of the CSPAEK membranes was analyzed using SAXS. The resulting membrane properties were well explained by the SAXS patterns.

Probing Polymer–Pendant Interactions in the Conducting Redox Polymer Poly(pyrrol-3-ylhydroquinone)

Conducting polymers with redox active pendant groups show properties typical of both conducting polymers (i.e., capacitive charging and intrinsic conductivity) and redox polymers (i.e., electrochem ...

Cationic polymer brush-modified cellulose nanocrystals for high-affinity virus binding.

Surfaces capable of high-affinity binding of biomolecules are required in several biotechnological applications, such as purification, transfection, and sensing. Therein, the rod-shaped, colloidal cellulose nanocrystals (CNCs) are appealing due to their large surface area available for functionalization. In order to exploit electrostatic binding, their intrinsically anionic surfaces have to be cationized as biological supramolecules are predominantly anionic. Here we present a facile way to prepare cationic CNCs by surface-initiated atom-transfer radical polymerization of poly(N,N-dimethylaminoethyl methacrylate) and subsequent quaternization of the polymer pendant amino groups. The cationic polymer brush-modified CNCs maintained excellent dispersibility and colloidal stability in water and showed a ζ-potential of +38 mV. Dynamic light scattering and electron microscopy showed that the modified CNCs electrostatically bind cowpea chlorotic mottle virus and norovirus-like particles with high affinity. Addition of only a few weight percent of the modified CNCs in water dispersions sufficed to fully bind the virus capsids to form micrometer-sized assemblies. This enabled the concentration and extraction of the virus particles from solution by low-speed centrifugation. These results show the feasibility of the modified CNCs in virus binding and concentrating, and pave the way for their use as transduction enhancers for viral delivery applications.

FRET-Assisted Deep-Blue Electroluminescence in Intercalated Polymer Hybrids

Polymer/layered silicate nanocomposites (PSNs), obtained through a bottom-up strategy with both free and intercalated poly(styrene) carrying fluorescent terfluorene side-chains, allow for the fabrication of optically transparent films with controlled morphology and fine-tuning of the organic/inorganic interface properties. The successful assessment of the hybrid material as an efficient emitter in a light-emitting device is reported, and the complex mechanism responsible for its emission is elucidated. The approach allows planarization and chemical and photostabilization of short intercalated oligo(fluorene)s whose emissive properties are enhanced thanks to exciton localization. Both photoluminescence and electroluminescence are assisted by a sensitization mechanism exploiting resonant energy transfer from nonplanar, nonintercalated polymer pendant conformers wrapping the silicates. A single-layer, solution-processable, hybrid light emitting diode (LED) displays deep-blue electroluminescence with a record external quantum efficiency, for this class of materials, of 1.2%, maximum luminance of 860 cd/m2, Commission Internationale de l’Eclairage (CIE) 1931 (x, y) chromaticity coordinates of (0.158, 0.114), and low efficiency roll-off thanks to the separation of the emissive region from the charge transport one.