Comb Copolymers Research Articles

Stability of negatively charged platelets in calcium-rich anionic copolymer solutions.

Controlling the stability of anisotropic particles is key to the development of advanced materials. Here, we report an investigation, by means of mesoscale molecular dynamics simulations, of the stability and structural change of calcium-rich dispersions containing negatively charged nanoplatelets, neutralized by calcium counterions, in the presence of either comb copolymers composed of anionic backbones with attached neutral side chains or anionic-neutral linear block copolymers. In agreement with experimental observations, small stacks of platelets (tactoids) are formed, which are greatly stabilized in the presence of copolymers. In the absence of polymers, tactoids will grow and aggregate strongly due to large attractive Ca(2+)-Ca(2+) correlation forces. Unlike comb copolymers which only adsorb on the external surfaces, block copolymers are found to intercalate between the platelets. The present results show that the stabilization is the result of a free energy barrier induced by the excluded volume of hydrophilic chains, while the intercalation is due to bridging forces. More generally, the results shed new light on the recent finding of the first hybrid cementitious mesocrystal.

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.

Construction of photoresponsive supramolecular micelles based on ethyl cellulose graft copolymer

In this work, a UV-Visible light controlled supramolecular system based on ethyl cellulose (EC) was constructed, combining the host-guest interaction of β-cyclodextrin (β-CD) group and trans-isomer of azobenzene (tAzo) group. To link β-CD to the hydrophobic section, renewable EC was used as macroinitiator to initiate the polymerization of ɛ-caprolactone (ɛ-CL) to form biocompatible and biodegradable comb copolymer EC-g-PCL, and β-CD was attached to the end of PCL side chain via click reaction. Meanwhile, hydrophilic PEG-tAzo was obtained by N,N′-dicyclohexylcarbodiimide (DCC) coupling. Then, the structures of the products were characterized by nuclear magnetic resonance (NMR) and gel permeation chromatography (GPC). Subsequently, with the formation of inclusion complexes by β-CD and tAzo groups, the obtained EC-g-PCL-β-CD/PEG-tAzo supramolecular system self-assembled in water with hydrophobic EC-g-PCL-β-CD as core and hydrophilic PEG-tAzo as shell. Furthermore, dynamic light scattering (DLS) and transmission electron microscopy (TEM) were utilized to investigate the particle size and size distribution, while NMR and UV-Vis spectra were applied to explore the UV-Visible light stimuli-responsiveness of the micelles.

Multifunctional comb copolymer ethyl cellulose-g-poly(ε-caprolactone)-rhodamine B/folate: Synthesis, characterization and targeted bonding application

Well-defined comb copolymer ethyl cellulose-g-poly(ε-caprolactone) (EC-g-PCL) with good biocompatibility and biodegradability was synthesized through ring-opening polymerization (ROP) using ethyl cellulose (EC) as backbone. EC-g-PCL was further modified with rhodamine B (RhB) and folate (FA) via coupling reactions to obtain EC-g-PCL-RhB/FA with fluorescence and targeting functionality. Nuclear magnetic resonance (NMR) and gel permeation chromatography (GPC) were applied to confirm the molecular structures of the comb copolymers. Thermogravimetric analyzer (TGA), differential scanning calorimeter (DSC) and polarized optical microscope (POM) were utilized to investigate the thermal and crystalline properties of EC-g-PCL-RhB/FA, which were distinct from the corresponding properties of EC-g-PCL without RhB and FA. The characteristic signals in UV–vis and fluorescence spectra demonstrated the capacity of EC-g-PCL-RhB/FA serving as fluorescent probe. Laser scanning confocal microscopy (LSCM) confirmed the bonding of EC-g-PCL20-RhB/FA to HeLa cells with FA as targeting ligand. Such multifunctional comb copolymer EC-g-PCL-RhB/FA has potential applications in the field of targeted drug release.

Synthesis and Characterization of Sequence-Controlled Semicrystalline Comb Copolymers: Influence of Primary Structure on Materials Properties

Sequence-controlled semicrystalline copolymers were prepared by nitroxide-mediated copolymerization of a large excess of octadecylstyrene with small amounts of functional N-substituted maleimides (i.e., N-(n-propyl)maleimide, N-benzylmaleimide, pentafluorophenyl 4-maleimidobenzoate, 4-(N-maleimido)azobenzene, N-(1-pyrenyl)maleimide, and N-(2-(amino-BOC)ethylene)maleimide). These copolymers were prepared in bulk at 110 °C using the commercial alkoxyamine BlocBuilder MA as initiator and control agent. Time-controlled additions protocols were used to place the N-substituted maleimides at precise chain location along the poly(octadecylstyrene) backbones. Size exclusion chromatography and 1H NMR studies indicated that well-defined copolymers with controlled monomer sequences, composition, chain length, and molecular weight distribution were formed in all cases. Although possessing an atactic backbone, these polymers exhibit a semicrystalline behavior. The electron diffraction method indicated that the octadecy...

Morphological Control for Aggregates of DNA Molecules Chemisorbed on the Organized Films of Ternary Comb Copolymers Containing <i>s</i>-Triazine Rings

We investigated adsorption behavior of DNA molecules to ternary comb copolymers containing 2-vinyl-4, 6-diamino-1, 3, 5-triazine (VDAT) at air/water interface and their molecular arrangement. A newly ternary comb copolymers as adsorption template was synthesized by radical copolymerization of VDAT, octadecyl acrylate (OA), 2-(perfluorodecyl)ethyl methacrylate (FF10EMA). The IR spectrum and UV-vis spectrum of transferred LB multilayers indicates adsorption of DNA molecules by ternary copolymer templates. There were hydrogenated domains at 40–50 nm diameter scales in phase separated surface structure of Z-type monolayers. Furthermore, adsorbed DNA molecules showed segment domain at 100–200 nm scales. Fluorescence emission bands of adsorbed DNA to copolymer film showed red-shift and became sharper than the one of their so lution. It was caused by formation of aggregate of π-conjugated system in the DNA with uniform aggregation number. In the case of copolymer film containing N-vinyl carbazole (NVCz), small domain at 30-40 nm scales and DNA aggregate with various aggregation number were confirmed.

Elucidation of Internal Fine Structure of "Polymer Nanosphere" in the Interfacial Particle Film

Transition behavior from a monolayer on the water surface to a single particle layer of a ternary comb copolymer with highly hydrophobic carbazole units and both hydrogenated and fluorinated side-chains have been investigated by surface pressure−area (π−A) isotherm and atomic force microscopic (AFM) observation. Moreover, we fabricated a polymer nanosphere multilayered organization consisting of such polymer nanoparticles by the Langmuir–Blodgett (LB) technique, and estimated the particle arrangement by performing out-of-plane X-ray diffraction (XRD) analysis. This polymer monolayer is able to form the polymer nanosheet with amorphous layers. The multiparticle layered organization of polymer nanosphere is fabricated from the single particle layer by the LB technique. These layer structures have highly regular arrangement along the c-axis. Further, we investigated molecular arrangement inside of polymer particles by performing in-plane XRD analysis and fluorescence spectroscopy. This copolymer formed side-chain crystals inside the particles. Fluorocarbon chains had a short spacing of 5.0 A for the two-dimensional side-chain lattice whereas hydrocarbon chains formed sub-cell at short spacing of 4.2 A. In addition, aggregated structure of carbazole rings is formed by π-π interaction.

Formation of aggregates of DNA molecules chemisorbed on the organized films of comb copolymers containing s-triazine

Adsorption behavior of DNA molecules on comb copolymers containing 2-vinyl-4,6-diamino-1,3,5-triazine (VDAT) at the air/water interface and their molecular arrangement were investigated using surface pressure–area (π–A) isotherms, infrared (IR) spectroscopy, polarized UV–vis spectroscopy, and atomic force microscopy (AFM). Newly hydrogenated and fluorinated binary comb copolymers containing VDAT as an adsorption template were synthesized by radical copolymerization. Based on the results of the π–A isotherm of the monolayer on DNA aqueous solution, an increase in the value of molecular area per VDAT unit corresponds to an area of 20Å2. The IR spectrum of the transferred Langmuir–Blodgett (LB) multilayer indicates adsorption of DNA molecules by hydrogen bonding to the copolymer templates. AFM images show that the circular domains have 50–60nm diameters. Adsorbed DNA molecules showed an absorption band at 260nm and emitted fluorescence at 400nm. Consistent with the results of polarized UV–vis spectroscopy, these absorption bands indicate weak polarized dependency. In addition, emission bands in the fluorescence spectrum of DNA adsorbed to the copolymer film showed red shift and became sharper than those of the DNA solution.

Thermosensitive mPEG-b-PA-g-PNIPAM Comb Block Copolymer Micelles: Effect of Hydrophilic Chain Length and Camptothecin Release Behavior

Block copolymer micelles are extensively used as drug controlled release carriers, showing promising application prospects. The comb or brush copolymers are especially of great interest, whose densely-grafted side chains may be important for tuning the physicochemical properties and conformation in selective solvents, even in vitro drug release. The purpose of this work was to synthesize novel block copolymer combs via atom transfer radical polymerization, to evaluate its physicochemical features in solution, to improve drug release behavior and to enhance the bioavailablity, and to decrease cytotoxicity. The physicochemical properties of the copolymer micelles were examined by modulating the composition and the molecular weights of the building blocks. A dialysis method was used to load hydrophobic camptothecin (CPT), and the CPT release and stability were detected by UV-vis spectroscopy and high-performance liquid chromatography, and the cytotoxicity was evaluated by MTT assays. The copolymers could self-assemble into well-defined spherical core-shell micelle aggregates in aqueous solution, and showed thermo-induced micellization behavior, and the critical micelle concentration was 2.96-27.64 mg L(-1). The micelles were narrow-size-distribution, with hydrodynamic diameters about 128-193 nm, depending on the chain length of methoxy polyethylene glycol (mPEG) blocks and poly(N-isopropylacrylamide) (PNIPAM) graft chains or/and compositional ratios of mPEG to PNIPAM. The copolymer micelles could stably and effectively load CPT but avoid toxicity and side-effects, and exhibited thermo-dependent controlled and targeted drug release behavior. The copolymer micelles were safe, stable and effective, and could potentially be employed as CPT controlled release carriers.

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...

Stereocomplex Formation in Polylactide Multiarm Stars and Comb Copolymers with Linear and Hyperbranched Multifunctional PEG

AbstractA systematic comparison between graft poly(l‐lactide) copolymers with different topologies and their ability to form stereocomplexes with poly(D‐lactide) (PDLA) is performed. Comb and hyperbranched copolymers based on functional poly(ethylene glycol) and poly(l‐lactide) with molecular weights in the range of 2000–90 000 g mol−1 and moderate molecular weight distributions (Mw/Mn = 1.08–1.37) are prepared via the combination of anionic and ring‐opening polymerization. Two “topological isomers,” a linear poly(ethylene oxide)/poly(glycerol) (PEG/PG) copolymer and a branched PEG/PG copolymer are used as backbone polymers. Furthermore, the stereocomplex formation between PDLA and the hyperbranched and comb copolymers containing poly(l‐lactide) arms is studied. Stereocomplex formation is confirmed by DSC as well as by Fourier transform IR (FTIR) and Raman spectroscopy.magnified image

128 Some derivatives of 1,3-diazaadamantane strongly stimulate strand exchange reaction between short oligonucleotides

Earlier, we characterized the behavior of HG122 (compound III) in the DNA Strand Exchange Reaction (SER) and found that 1,3-diazaadamantane derivative facilitates SER in the system of short oligonucleotides (Gabrielian et al., 2011). In the present study, a series of new derivatives of 1,3-diazaadamantane have been synthesized with the purpose to discern how small variations in the compound structure can influence its activity in SER and try to get more effective substances for stimulation of SER. We revealed that most of the small variations in the structure significantly influenced the compounds’ efficacy in accelerating SER. For example, an increase in the compounds’ aliphatic chain lengths considerably enhanced its efficiency in SER stimulation and in the series of compounds presented in the Figure HG188 (compound IV) was eminently the most potent agent in the stimulation of SER. Small modifications in other parts of the 1,3-diazaadamantane molecule also influenced the SER stimulation and several derivatives more efficient in facilitating SER than HG122 were revealed. Some of the compounds exhibited virtually negligible capability to stimulate SER but, interestingly, out of 12 derivatives characterized, agents that retard spontaneous SER were not found. Earlier, the stimulation of the DNA strand exchange was documented for different ligands of the policationic nature such as Cationic Comb Copolymers (Kim et al., 2003), linker histones (Bocharova et al., 2012), cobalt hexamine (unpublished observation) etc. The present results provide us with a novel class of SER facilitating compounds – the cationic amphiphiles that can serve as interesting objects for further understanding of different aspects of DNA SER. Biomedical implications and prospects in biomedical applications of these and similar compounds’ activity in SER remain to be investigated.

Fabrication and Structural Estimation of “Polymer Nanosphere Multilayered Organization”

We have newly constructed “multi-particle layered organization” of aromatic polyamide (poly-(N- alkylated benzamide), abbrev . PABAn , n : carbon number of side-chains) derivatives having both a rigid main chain and a flexible side chains by a Langmuir-Blodgett (LB) technique. This organization is composed of the build-up particle layers with highly regular arrangement along the c -axis. The particle arrangement of this organization of polymer nanosphere was estimated by performing out-of plane X-ray diffraction (XRD), and atomic force microscopic (AFM) observation. In addition, it is also proposed that ternary comb copolymers with carbazole units and both hydrogenated and fluorinated side-chains are candidates of newly typed “polymer nanosheet” material. These copolymers with high hydrophobic carbazole contents also formed single particle layer at air/water interface and “multi-particle layered organization” was constructed by a LB technique. Therefore, it was found that “multi-particle layered organization of polymer nanosphere” and “polymer nanosheet” are simultaneously formed by same component copolymer materials with hydrophobic carbazole units.

Superhydrophobic surfaces fabricated by spray-coating micelle solutions of comb copolymers

A series of comb copolymers (poly(arylene alkylene ether) (FPAE)-polystyrene (PS)) with a highly fluorinated FPAE main chain and narrow dispersed PS-grafted chains have been prepared. They are used to prepare micelle solutions in methanol/acetone (M/A) mixed solvents which are good for the FPAE main chains and poor for the PS-grafted chains. In these solutions, the PS-grafted chains form the cores and the FPAE main chains form the corona layers of micelle particles. Uniform micelle particles are achieved because of the narrow molecular weight dispersion of the PS chain length. The micelle solutions are spray-coated onto glass substrates to fabricate hydrophobic surfaces. It is found that the stability of the micelle particles increases with the length of the PS-grafted chains, which further influences the morphology and hydrophobicity of the spray-coated films. The effects of the M/A ratio and the copolymer concentration on the morphology and hydrophobicity of the coating surfaces are also studied. The results prove that a binary nano/microsurface structure is important to achieve a superhydrophobic surface with a low contact angle hysteresis. This binary structure is formed from conglomeration of micelle particles by spray coating the micelle solutions. The best sample reported in this paper has a static contact angle of 163° and a sliding angle of 5.9°. This fabrication procedure is facile, less time consuming, and easily applicable for large-scale surface treatment.

Morphological Transition from Nanosheet to Nanosphere in Ternary Comb Copolymers with Carbazole Rings

Abstract The transition behavior of ternary comb copolymers containing carbazole rings from a monolayer on a water surface to a single particle layer has been investigated by surface pressure–area isotherms and atomic force microscopy. It has been found that these copolymers form a monolayer in the low-surface-pressure region and a single particle layer in the high-surface-pressure region.

PH-responsive drug delivery systems based on clickable poly(L-glutamic acid)-grafted comb copolymers

Five pH-responsive alkyne-poly(2-aminoethyl methacrylate)-graft-poly(L-glutamic acid) (alkyne-PAMA-g-PLGA) comb copolymers were synthesized through the ring-opening polymerization (ROP) of γ-benzyl-L-glutamate N-carboxyanhydride (BLG NCA) and the subsequent deprotection of benzyl group from BLG unit. The chemical structures of copolymers were confirmed by proton nuclear magnetic resonance spectra (1H NMR) and Fourier transform infrared spectroscopy (FTIR). The pyrene-probe-based fluorescence technique and transmission electron microscopy (TEM) measurements revealed that the comb copolymers could spontaneously self-assemble into micellar or vesicular nanoparticles in phosphate buffered saline (PBS) at pH 7.4. Doxorubicin (DOX), an anthracycline anticancer drug, was loaded into nanoparticles as a model anticancer drug. The in vitro release results showed that the release behaviors could be altered by adjusting the composition of the comb copolymer and pH of the release medium. In vitro methyl thiazolyl tetrazolium (MTT) assays demonstrated that the copolymers were biocompatible, and DOX-loaded nanoparticles showed effective inhibition of cellular proliferation. Hemolysis tests indicated that the copolymers were also hemocompatible, and that the presence of the copolymers could reduce the hemolysis ratio (HR) of the DOX significantly. In addition, the comb copolymers could be modified through versatile Cu(I)-catalyzed “click chemistry” between the terminal alkyne group and azide-modified functional agents. These properties indicate that the pH-responsive clickable comb copolymers are promising candidates for multifunctional nanocarriers in cancer diagnosis and therapy. Open image in new window

Interaction of polymethacrylate-g-PEO comb copolymers with natural bentonite in aqueous systems

Natural bentonite was successfully modified using polymethacrylate-g-polyethylene oxide (PEO) comb copolymer. Changes in the surfaces and microstructure of the resultant organo-bentonite were characterised by Fourier transform infrared (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TG), scanning electron microscopy and high-resolution transmission electron microscopy, respectively. FTIR results indicated the presence of the copolymer on the surface of organo-bentonite. XRD measurements showed that the copolymer molecules were intercalated into the bentonite layers. TG analysis and electron microscopy micrographs demonstrated the interlayers of bentonite were intercalated by the copolymers with surface adsorption to a certain extent.

Organometallic polymeric carriers for redox triggered release of molecular payloads

The synthesis and characterization of a novel redox responsive comb-copolymer consisting of a poly(ferrocenylsilane) backbone and N-dimethylethyl ammonium and N-dimethyldecyl ammonium substituents are reported. Due to the presence of the side groups featuring cationic amine as well as decyl hydrocarbon chains the comb copolymer exhibits amphiphilic behaviour and forms micellar assemblies with typical dimensions of 100 nm. The assemblies display unique, redox induced morphology change in water, investigated by dynamic light scattering and transmission electron microscopy. Paclitaxel and Nile Red were encapsulated in the micelles as model guest molecular payloads. Release of the guests with a high degree of profile control by varying the concentration of redox agents is presented.

Control of Arrangement for DNA Molecules Chemisorbed to the Organized Molecular Films of Comb Copolymers Containing <i>s</i>-Triazine

Adsorption behavior of DNA molecules to comb copoly mers containing 2-vinyl-4, 6-diamino-1, 3, 5-triazine (VDAT) at air/water interface and their molecular arrangement have investigated by surface pressure-area (π-A) isotherm, IR spectroscopy, pola rized UV-vis spectroscopy, and atomic force microscopy. A newly hydrogenated and fluorinated b inary comb copolymers containing VDAT as adsorption template was synthesized by radical copo lymerization. From the result of π-A isotherm of monolayer on DNA aqueous solution, an increase of v alue for molecular area per VDAT unit corresponds to 20 A 2 . The IR spectrum of transferred LB multilayer ind icates adsorption of DNA molecules by hydrogen bonding to the copolymer templates. AFM images sho w the circular domain at 50-60 nm diameters. Adsorbed DNA molecules showed the absorption band a t 260 nm and emitted fluorescence at 400 nm. From the results of polarized UV-vis spectroscopy, these absorption bands indicate faint polarized dependency. In addition, emission bands in fluores cence spectrum of adsorbed DNA to copolymer film showed red-shift and became sharper than the one of their solution.

Morphological Transition from Nanosheet to Nanosphere of Ternary Comb Copolymers with Carbazole Rings Induced by an Increase in Surface Pressure

Fax: +81-48-858-3503, e-mail: fujimori@fms.saitama-u.ac.jp Transition behavior from a monolayer on the water surface to a single particle layer of a ternary comb copolymer containing carbazole rings have been investigated by surface pressure-area isotherm, atomic force microscopy, X-ray diffraction. This polymer monolayer is able to form the “polymer nanosheet” with amorphous layers and strong interaction between main-chains prepared by the Langmuir-Blodgett (LB) technique. Further, the single particle layer is able to form the multi-particle layered organization of “polymer nanosphere” by the LB technique. This ternary comb copolymers were synthesized by radical copolymerization with hydrogenated and fluorinated long-chain vinyl compounds. Poly(N-vinylcarbazole) homopolymer formed a single particle layer on the water surface immediately after spreading. Spontaneous “particulation” behavior is accelerated by incorporation of carbazole units in ternary copolymer films. Organized molecular film of these copolymers formed a monolayer on the water surface below 10 m Nm