Amphiphilic Comb Polymer Research Articles

Superparamagnetic Nanoparticles with Phosphorescent Complexes as Hybrid Contrast Agents: Integration of MRI and PLIM

Two different hybrid nanosystems are prepared by loading highly crystalline, monodisperse magnetite nanocubes (MNCs) with phosphorescent Pt(II) complexes (PtCxs). One involves the encapsulation of the hydrophobic PtCx1 within an amphiphilic comb polymer (MNC@poly(maleic anhydride‐alt‐1‐octadecene) [PMAO]–PtCx1), whereas the other involves the direct binding of the hydrophilic PtCx2 to the surface of the MNC mediated by a ligand‐exchange procedure (MNC@OH–PtCx2). Both systems are evaluated as potential candidates for multimodal imaging in magnetic resonance imaging (MRI) and photoluminescence lifetime imaging micro(spectro)scopy (PLIM). PLIM measurements on agarose phantoms demonstrate significantly longer excited‐state lifetimes compared to the short‐lived autofluorescence of biological background. Additionally, both nanosystems perform as effective MRI contrast agents (CAs): the r2* values are 3–4 times higher than for the commercial CA ferucarbotran. MNC@PMAO–PtCx1 particles also cause significant increases in r2. While the ligand exchange procedure efficiently anchors PtCxs to the MNC surface, the polymeric encapsulation ensures higher colloidal stability, contributing to differences in PLIM and MRI outcomes. In these results, the successful integration of two complementary noninvasive imaging modalities within a single nanosystem is confirmed, serving as the impetus for further investigation of such systems as advanced multimodal–multiscale imaging agents with dual orthogonal readouts.

Ionic Combisomes: A New Class of Biomimetic Vesicles to Fuse with Life.

The construction of biomembranes that faithfully capture the properties and dynamic functions of cell membranes remains a challenge in the development of synthetic cells and their application. Here a new concept for synthetic cell membranes based on the self‐assembly of amphiphilic comb polymers into vesicles, termed ionic combisomes (i‐combisomes) is introduced. These combs consist of a polyzwitterionic backbone to which hydrophobic tails are linked by electrostatic interactions. Using a range of microscopies and molecular simulations, the self‐assembly of a library of combs in water is screened. It is discovered that the hydrophobic tails form the membrane's core and force the backbone into a rod conformation with nematic‐like ordering confined to the interface with water. This particular organization resulted in membranes that combine the stability of classic polymersomes with the biomimetic thickness, flexibility, and lateral mobility of liposomes. Such unparalleled matching of biophysical properties and the ability to locally reconfigure the molecular topology of its constituents enable the harboring of functional components of natural membranes and fusion with living bacteria to “hijack” their periphery. This provides an almost inexhaustible palette to design the chemical and biological makeup of the i‐combisomes membrane resulting in a powerful platform for fundamental studies and technological applications.

Control of phase-separated morphology in mixed monolayers of amphiphilic comb polymers containing diamino-s-triazine and non-amphiphilic s-triazine derivatives with fluorocarbons

In this study, s-triazine rings (or their derivatives) were introduced into a two-dimensional phase-separated mixed monolayer of hydrocarbon-fluorocarbon chains. The diamino-triazine ring facilitated the absorption of deoxyribonucleic acid (DNA) molecules in the mixed monolayer. The diamino s-triazine ring-containing copolymers into which a hydrogenated hydrophobic chain was introduced were able to form mixed-phase-separated monolayers when combined with an s-triazine ring-containing fluorocarbon-based molecule with low molecular weight having no hydrophilic group. Hydrocarbon-based copolymers that formed side-chain crystals in the single-component monolayer influenced the steric hindrance of the diamino s-triazine ring and tended to be amorphous in the mixed film. However, the regularity along the c-axis direction was guaranteed, and introducing long-chain alkylated amphiphilic molecules enhanced the crystallinity and promoted the formation of circular domains. Comparatively, the fluorocarbon, which was amorphous in the single-component monolayer, promoted two-dimensional crystallization by enhancing the π-π interaction between the s-triazine rings in the phase-separated monolayer.

Hydrophilization of magnetic nanoparticles with an amphiphilic polymer revisited: Roles of nanoparticle capping density and polymer structure

Amphiphilic comb polymers, like poly(maleic anhydride-alt-1-octadecene) (PMAO), are frequently used to transfer hydrophobic magnetic nanoparticles (NPs) into aqueous media. While it is accepted that the hydrophilization is based on the interdigitation of the hydrocarbon chains from the polymer and the NP capping, the factors that determine the success of such process are still not fully understood. In this paper, some key aspects of the formation of water-soluble NP-PMAO assemblies from oleate-capped iron oxide NPs, not considered in previous works, are discussed thoroughly. We have found that the process is notably hindered when the chemisorbed oleates coverage decreases from 2.9 to 1.5 molecules/nm2, revealing the importance of the capping packing density in the assembly mechanism. Combined results from small-angle x-ray scattering and electron microscopy show that, for polymer concentrations ranging from 10 to 200 monomer units/nm2, the NPs are individually covered by polymer chains, although forming rather planar NP-PMAO assemblies which contain several NPs. Both the minimum polymer concentration needed for a successful hydrophilization (0.7 gPMAO/L) and the geometry of the assemblies suggest that intermolecular structures typical of comb polymers act as templates in the assembly process. Finally, we show that the magnetic properties are modulated by the polymer loading.

Amphiphilic Comb Polymers as New Additives in Bicontinuous Microemulsions

It has been shown that the thermodynamics of bicontinuous microemulsions can be tailored via the addition of various different amphiphilic polymers. In this manuscript, we now focus on comb-type polymers consisting of hydrophobic backbones and hydrophilic side chains. The distinct philicity of the backbone and side chains leads to a well-defined segregation into the oil and water domains respectively, as confirmed by contrast variation small-angle neutron scattering experiments. This polymer–microemulsion structure leads to well-described conformational entropies of the polymer fragments (backbone and side chains) that exert pressure on the membrane, which influences the thermodynamics of the overall microemulsion. In the context of the different polymer architectures that have been studied by our group with regards to their phase diagrams and small-angle neutron scattering, the microemulsion thermodynamics of comb polymers can be described in terms of a superposition of the backbone and side chain fragments. The denser or longer the side chain, the stronger the grafting and the more visible the brush effect of the side chains becomes. Possible applications of the comb polymers as switchable additives are discussed. Finally, a balanced philicity of polymers also motivates transmembrane migration in biological systems of the polymers themselves or of polymer–DNA complexes.

Flexible, all-solid-state 1.4 V symmetric supercapacitors with high energy density based on comb polymer electrolyte and 1D hierarchical carbon nanotube electrode

A high-performance solid-state supercapacitor (ssSC) based on an amphiphilic comb polymer (CP) solid electrolyte and an electrode comprising porous one-dimensional (1D) hierarchical carbon nanotubes is reported. The solid electrolyte is prepared from the amphiphilic CP, poly(vinylidene fluoride-co-chlorotrifluoroethylene)-g-poly(oxyethylene methacrylate) (P(VDF-co-CTFE)-g-POEM) comprising hydrophobic P(VDF-co-CTFE) main chains and hydrophilic POEM side chains, which provide good mechanical strength and high ionic conductivity, respectively. Preferential interaction of POEM with the ionic liquid (IL) and microphase-separated structures of CP/IL electrolytes are demonstrated. Two types of 1D hierarchical carbon nanotubes are prepared by a metal–organic-framework-derived approach using 1D tellurium as the template. The ssSC fabricated with the CP electrolyte displays a high specific capacitance of 239.3 F g−1, which is much higher than that achieved with the widely used conventional poly(vinyl alcohol) electrolytes. The flexible ssSC fabricated with carbon cloth as electrode substrate exhibits a remarkable specific capacitance of 220.8 F g−1.

MgCO3-crystal-containing mixed matrix membranes with enhanced CO2 permselectivity

A cost-effective, facile method for simultaneously improving the CO2 permeance and CO2/N2 selectivity of mixed matrix membranes (MMMs) was developed using commercially available MgCO3 microcrystals. The MgCO3 crystals were broken into small pieces and homogenously dispersed in polymer matrices via mechanical stirring to form MMMs. In particular, an amphiphilic comb polymer (CP) composed of poly(ethylene glycol) behenyl ether methacrylate (PEGBEM) and poly(oxyethylene methacrylate) (POEM), i.e., PEGBEM–POEM, was found to be an effective matrix due to the specific interactions between its carbonyl oxygen atoms and MgCO3. The detailed interactions, morphologies, and structures of MgCO3 and CP/MgCO3 hybrids were characterized using scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM), N2 adsorption-desorption isotherm measurements, wide-angle X-ray scattering (WAXS), differential scanning calorimetry (DSC), and Fourier transform infrared (FT-IR) and Raman spectroscopies. The CP/MgCO3 MMM with 45wt% MgCO3 exhibited the highest CO2/N2 selectivity of 93.8 and CO2 permeance of 30.9 GPU (1GPU=10−6cm3(STP)/(s·cm2·cmHg)). This performance surpasses other MgCO3 MMMs prepared using commercially available polymers such as PEBAX® (a polyether block amide) and poly(ethylene oxide) (PEO). The improved performance resulted from the enhanced CO2 solubility by MgCO3 crystals, as confirmed by the CO2 uptake measurements.

Functionalization of emissive conjugated polymer nanoparticles by coprecipitation: consequences for particle photophysics and colloidal properties

The functionalization of polyfluorene (PFO) nanoparticles by coprecipitation of the conjugated polymer with an amphiphilic comb polymer, consisting of a hydrophobic polystyrene backbone with hydrophilic, carboxylic acid-terminated polyethylene oxide side-chains (PS-PEG-COOH), is investigated. The comb polymer affects the properties of the formed hybrid nanoparticles. Non-functionalized particles are typically larger (28 nm) than functionalized ones (20 nm); peak molar extinction coefficients are found to differ in a similar trend. Zeta potentials are negative, consistent with negative surface charge on PFO particles due to chemical defect formation, with additional charge on functionalized particles due to the pendant carboxylic acid groups. Emission quantum yields of functionalized particles are typically larger, consistent with lower efficiency of energy transfer to quenchers in smaller particles and weaker PFO interchain interactions due to chain dilution. The trend in per-particle fluorescence brightness values, as confirmed by single particle fluorescence imaging, reflects the nanoparticle extinction coefficients. Photostability studies on aqueous dispersions of hybrid particles indicate mild photobrightening under continuous illumination while PFO particles exhibit slow exponential emission decay. Functionalized particles are also resistant to aggregation during exposure to adenocarcinoma cells. Generally, the hybrid particles exhibit more favorable time-, pH- and medium-dependent stabilities, likely due to steric and electrostatic stabilization by PEG-carboxylic acid functionalities. Overall, the functionalized particles exhibit attractive properties: Reasonably small size, tight size distribution, high absorption cross section, radiative rate and emission quantum yield, excellent brightness and photostability, and good colloidal stability.

Efficient resolution of 3-phenoxy-1,2-propanediol by immobilized lipase on amphiphilic comb polymer modified TiO2

• The comb polymer modified TiO 2 was first applied for immobilization of lipase. • Greatly improved activity of immobilized lipase was obtained in all tested solvents. • Strict enantioselectivity of the immobilized lipase was achieved in all tested solvents. An amphiphilic microenvironment is a key element to the lipase which catalyzes substrates at the aqueous and hydrophobic interface. An amphiphilic comb copolymer, poly(sodium acrylate)- g -methoxy poly(ethylene oxide), was introduced for the post-functionalization of mesoporous TiO 2 . The lipase from Burkholderia ambifaria YCJ01 was immobilized on the comb copolymer modified TiO 2 . The activity of immobilized lipase YCJ01 showed that comb polymer which side chain with a molecular weight of 1000 was the best material for the functionalization of TiO 2 . The amount of adsorbed lipase was 55.6 mg/g support and the immobilized lipase activity was 6076.1 U/g support. It was worth to note that the immobilized lipase achieved more than 200% of its origin activity in hydrophobic solvents and very stable in hydrophilic solvents. The immobilized lipase was used as a catalyst for resolution of 3-phenoxy-1,2-propanediol, and showed high enantioselectivity ( ee p ≥ 99%) in all tested organic solvents. This might be explained that comb polymer with amphiphilic, multiple side chains features could well stabilize the favorite active conformation of lipase to the resolution substrate in all tested organic solvents. In diisopropyl ether reaction solvent, the yield of 49.8% and an enantiomeric excess of 99.2% for S -diacetate were achieved after one operation, and maintained relative yield of 72% for S -diacetate even after six reaction cycles with no significant decrease in the enantiomeric excess of product.

Morphologically induced polychromism of MEH-PPV nanoparticles prepared using amphiphilic comb-polymer as encapsulation matrix

Control over the photophysical properties of aqueous dispersions of conjugated polymers is of interest for biosensing and bioimaging applications and of paramount importance in the fabrication of optoelectronic devices. We demonstrate that an amphiphilic comb-polymer obtained from a poly(maleic anhydride-alt-1-octadecene) precursor can be used as effective transfer agent to bring hydrophobic poly[2-methoxy-5-(2′-ethylhexyloxy)-p-1,4-phenylenevinylene] (MEH-PPV) from the organic to the aqueous phase. Both the reprecipitation and miniemulsion methods results in MEH-PPV dispersed in water. The reprecipitation method results in bathochromically shifted emission relative to the emission of MEH-PPV in tetrahydrofuran. However, the miniemulsion method results in a hypsochromic shift in the emission of MEH-PPV relative to the emission of the polymer in chloroform.

Production of stable quinine nanodispersions using esterified γ-polyglutamic acid biopolymer

Novel methods are needed for the development of nanodispersed drug formulations to enhance bioavailability of many hydrophobic pharmaceuticals. The poorly water-soluble quinine is a well-known anti-malaria drug which can be used as a promising model compound for the development of novel nanodispersed formulations. In addition to hydrophobic drug's own affecting properties, surfactants play an important role for the enhancement of their low bioavailability by preparing stable dispersions. Amphiphilic compounds can efficiently be used to stabilize colloidal fragments by preventing the precipitation or crystallization of poorly water-soluble active ingredients during fabrication. A novel biopolymer derivative based on the biotechnologically produced γ-polyglutamic acid (γ-PGA) from Bacillus licheniformis cultivation was developed for encapsulation of the active ingredient. High-molecular γ-PGA is an anionic polyelectrolyte that was optimized and modified with hydrophobic l-phenylalanine ethyl ester (l-PAE) to form an amphiphilic comb polymer P(γ-GA-r-l-PAE) with surfactive properties. The approach of the nanodispersion polymer concentration, molecular weight and grafting degree enables the efficient stabilization of the poorly water-soluble model drug. The research presented in this report indicates the potential benefits of hydrophobically modified γ-PGA and suggests its potential role in forming stable dispersions for future pharmaceutical applications.

Enhancing the anti-fouling property of the SWRO membrane through the surface coating with the Styrene-PEGA copolymer

Polyamide-based reverse osmosis membranes have been used as a wastewater treatment process in recent years. However, natural organic materials present in the filtration medium cause severe membrane fouling problem, which makes the system less competitive. It is well known that membrane fouling can be influenced by the surface property of the membrane — surface morphology, chemical composition, surface charge, etc. To introduce hydrophilic materials on the membrane is one of the promising modification methods to mitigate membrane fouling. In this study, we investigated the effect of amphiphilic comb polymer coating layer on anti-fouling property of seawater reverse osmosis (SWRO) membranes. Styrene-PEGA amphiphilic copolymer was synthesized by a free radical solution polymerization method. The chemical structure and properties of the synthesized styrene-PEGA copolymer were determined by Fourier transform-infrared spectroscopy (FT-IR), atomic force microscopy (AFM), and ξ-potential. Obtained copolymer was coated on the membrane surface via a simple dipping method. The performance of the coated membrane was evaluated in a cross flow mode. The anti-fouling property of the surface coated membrane was investigated using model foulant solution filtration. Bovine serum albumin was used as a model foulant. The modified membranes were less fouled than pristine RO membranes, and recovered 95% of its initial flux after hydraulic cleaning.

Antifouling poly(vinylidene fluoride) ultrafiltration membranes containing amphiphilic comb polymer additive

AbstractAn amphiphilic comb polymer consisting of poly(vinylidene fluoride‐co‐chlorotrifluoroethylene) [P(VDF‐co‐CTFE)] main chains and poly(oxyethylene methacrylate) (POEM) side chains was synthesized using direct initiation of the chlorine atoms in CTFE units through atom transfer radical polymerization, as confirmed by 1H NMR and FTIR spectroscopy. The P(VDF‐co‐CTFE)‐g‐POEM comb polymer was introduced as an additive to prepare poly(vinylidene fluoride) antifouling ultrafiltration membranes. As the contents of comb polymer increased, the mechanical properties of membranes slightly decreased due to the decreased crystallinity of the membranes, as revealed by universal testing machine and X‐ray diffraction. However, water contact angle measurement and X‐ray photoelectron spectroscopy showed that the hydrophilic POEM segments spontaneously segregated on the membrane surfaces. As a result, the antifouling property of the membranes containing P(VDF‐co‐CTFE)‐g‐POEM comb polymer was considerably improved with a slight change of water flux. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 183–189, 2010

Synthesis and characterization of AgBr nanocomposites by templated amphiphilic comb polymer

A novel amphiphilic graft copolymer, poly(vinylidene fluoride- co-chlorotrifluoroethylene)- g-poly(4-vinyl pyridine) (P(VDF- co-CTFE)- g-P4VP) at 65:35 wt.%, respectively, was synthesized via atom transfer radical polymerization (ATRP), as confirmed by nuclear magnetic resonance ( 1H NMR) and transmission electron microscopy (TEM). Silver bromide (AgBr) nanoparticles were in situ generated within the self-assembled P(VDF- co-CTFE)- g-P4VP graft copolymer. TEM, UV–visible spectroscopy and X-ray diffraction (XRD) analyses support the successful formation of P(VDF- co-CTFE)- g-P4VP nanocomposites consisting of stabilized AgBr nanoparticles mostly 20–40 nm in size, which is presumably due to the capping action of the coordinating pyridine groups of the graft copolymer. The wavenumber of pyridine nitrogen in FT-IR spectra and the glass transition temperature ( T g) of the graft polymer measured by DSC shifted upon the formation of AgBr nanoparticles, indicating specific interactions between the nanoparticles and the graft copolymer matrix.

Restriction of biofouling in membrane filtration using a brush-like polymer containing oligoethylene glycol side chains

We investigated the effect of an amphiphilic comb polymer on reducing nonspecific adsorption of biomolecules in membrane filtration. The amphiphilic comb polymer is a methyl methacrylate-based coating material with short nonfouling oligoethylene glycol side chains that provides long-term, bio-repellant surfaces. The nonfouling property of this polymer on a commercially available filtration membrane was observed through cyclic filtration–washing processes of microbial, alginic acid, and bovine serum albumin solutions. The chemical structure and properties of the synthesized comb polymer were determined by Fourier transform-infrared spectroscopy (FT-IR), nuclear magnetic resonance (NMR), X-ray photoelectron spectroscopy (XPS), and gel permeation chromatography (GPC), while the permeation characteristics of the hydrophobic polysulfone membrane and comb polymer coated membranes were examined using home-built ultrafiltration cross-flow sets. Membranes coated with the comb polymer showed higher flux recovery than control membranes after a five-cycle filtration–washing process. Taken together, this shows that the comb polymer effectively inhibits the fouling of membrane surfaces by biomolecular materials.

Pretreatment of Amphiphilic Comb Polymer Surfaces Dramatically Affects Protein Adsorption

New applications in regenerative biotechnology require the ability to understand and control protein-surface interactions on micrometer and submicrometer length scales. Evidence presented here shows that micropatterned amphiphilic comb polymer films exhibit a pretreatment-dependent behavior with respect to protein adsorption for the proteins fibronectin, laminin, and for serum. A micropatterned surface, consisting of protein-reactive regions, separated by comb polymer, was created and tested for protein adsorption using the surface-sensitive imaging tool TOF-SIMS. Immersion of micropatterned surfaces in solutions of fibronectin or laminin resulted in uniform protein coverage on both the comb polymer and protein-reactive regions. However, preimmersion of similarly patterned surfaces in water for 2 h prior to protein incubation was found to dramatically improve the protein-resistant properties of the comb polymer regions. These results are consistent with poly(ethylene glycol) (PEG) side chain reorientation and/or hydration and poly(methyl methacrylate) (PMMA) backbone segregation away from the interface region.

Fabrication of Biofunctionalized Quasi-Three-Dimensional Microstructures of a Nonfouling Comb Polymer Using Soft Lithography

This paper describes a simple set of patterning methods that are applicable to diverse substrates and allow the routine and rapid fabrication of protein patterns embedded within a background that consists of quasi-three-dimensional microstructures of a cell-resistant polymer. The ensemble of methods reported here utilizes three components to create topographically nonfouling polymeric structures that present cell-adhesive protein patterns in the regions between the microstructures: the first component is an amphiphilic comb polymer that is comprised of a methyl methacrylate backbone and pendant oligo(ethylene glycol) moieties along the side chain, physically deposited films of which are protein- and cell-resistant. The second component of the fabrication methodology involves the use of different variants of soft lithography, such as microcontact printing to create nonfouling topographical features of the comb polymer that demarcate cell-adhesive regions of the third component: a cell-adhesive extracellular protein or peptide. The ensemble of methods reported in this paper was used to fabricate quasi-three-dimensional patterns that present topographical and biochemical cues on a variety of substrates, and was shown to successfully maintain cellular patterns for up to two months in serum-containing medium. We believe that this, and other such methods under development that allow independent and systematic control of chemistry, topography and substrate compliance will provide versatile “test-beds” for fundamental studies in cell biology as well as allow the discovery of rational design principles for the development of biomaterials and tissue-engineering scaffolds.

Surface engineering strategies for control of protein and cell interactions

Surface engineering is an important tool in understanding the molecular mechanism of protein adsorption and cell-surface interactions with the aim of rational design of surfaces for different biological applications. This article first briefly summarizes some of the commonly used approaches to control biological interactions at the solid–water interface. Next, two different approaches are presented from the authors’ research to engineer surfaces that address some of the problems and limitations of current approaches to modulate protein adsorption at surfaces. The first, “static” strategy involves modifying a surface with an amphiphilic comb polymer that presents short oligoethylene glycol side-chains. Two different fabrication methods to synthesize these non-fouling coatings are described including spin-coating and surface-initiated polymerization. The second, “active” strategy to control protein adsorption involves grafting a stimuli-responsive biopolymer, derived from an oligomeric sequence found in mammalian elastin to a surface. This polypeptide exhibits a lower critical solution temperature (LCST) transition in aqueous solution. Surfaces grafted with these polypeptides exhibit a hydrophilic-hydrophobic transition in response to increased temperature or salt concentration. The change in the interfacial properties can be exploited to create “active” polymer grafts that enable reversible, triggered binding of proteins onto surfaces in response to an external stimulus.

Universal Route to Cell Micropatterning Using an Amphiphilic Comb Polymer

Long‐term, spatially resolved attachment and growth of mammalian cells in a biologically relevant milieu on a variety of substrates is possible using the micropatterning techniques presented here (see cover). Two general methods, both involving microcontact printing of an amphiphilic comb polymer (see Figure) and incubation with a protein‐containing solution are reported.

Preparation of pH-responsive polymer membranes by self-organization

Self-organizing blends of poly(vinylidene fluoride) (PVDF) and an amphiphilic comb polymer having a PVDF backbone and poly(methacrylic acid) (PMAA), side chains are examined as a means to prepare membranes with pH-responsive separation characteristics. X-ray photoelectron spectroscopy analysis of membranes prepared from these blends indicates substantial surface segregation of the comb polymer during the standard immersion precipitation process for membrane fabrication, such that a near-surface coverage of 29 wt.% PMAA is achieved on membranes containing 10 wt.% comb (5 wt.% PMAA). Fluorescence microscopy studies on membrane cross-sections further reveal surface expression of PMAA on internal pore channel surfaces throughout the membrane. Membranes cast from these blends exhibit a reversible, pH-dependent flux variation of over an order of magnitude as the feed solution pH is varied between 2 and 8. The pH-dependent conformational changes of the PMAA surface layer are confirmed by force microscopy. These results demonstrate that “smart”, environmentally responsive (ER) membranes can be prepared by immersion precipitation with no post-coagulation processing steps.