Solutions Of Graft Copolymers Research Articles

Production of Graft Copolymers of Cod Collagen with Butyl Acrylate and Vinyl Butyl Ether in the Presence of Triethylborane-Prospects for Use in Regenerative Medicine.

Collagen is a suitable material for regenerative medicine because it is characterized by its good biocompatibility. However, due to its fibrillar structure, it cannot organize itself into three-dimensional porous structures without additional modification. The introduction of synthetic monomer elements into the collagen macromolecules is a technique used to form three-dimensional, collagen-based, branched, and crosslinked structures. New types of graft copolymers made from cod collagen with a butyl acrylate and vinyl butyl ether copolymer in aqueous dispersion were obtained in the presence of triethylborane by a radical mechanism. The process of graft copolymer formation proceeded as usual by radical initiation, through radicals formed during triethylborane oxidation by oxygen residues, collagen borination, and reversible inhibition with the participation of a boroxyl radical. The characteristics of the graft copolymers were determined using methods of physical and chemical analysis (GPC, SEM, IR spectroscopy, etc.), while the cytotoxicity was assessed using the MTT assay method. It is shown that the grafting of alternating blocks of butyl acrylate and vinyl butyl ether to the protein macromolecules results in changes in the morphological pattern of the graft co-polymer in comparison with native collagen. This is manifested in the development of consolidations around the collagen fibers of the structural matrices, with the co-polymer cellular structure consisting of interpenetrating pores of unequal size. Additionally, it is important that the graft co-polymer solutions are not toxic at a certain concentration. The above properties confirm the promising nature of the technique's application as the basis for producing new materials for regenerative medicine.

Structure and Dynamics of Inhomogeneities in Aqueous Solutions of Graft Copolymers of N-Isopropylacrylamide with Lactide (P(NIPAM-graft-PLA)) by Spin Probe EPR Spectroscopy.

Coil-to-globule transition and dynamics of inhomogeneities in aqueous solutions of graft copolymers of NIPAM with different content of oligolactide groups were studied using spin probe continuous wave EPR spectroscopy. The technique of the suppressing of TEMPO as spin probe by spin exchange with Cu2+ ions was applied. This approach allowed us to detect individual EPR spectra of the probe in collapsed globules and estimate its magnetic and dynamic parameters reliably. The formation of inhomogeneities at temperatures lower than the volume phase transition temperature measured via transmission, and differential scanning calorimetry was fixed. An increase in oligolactide content in copolymers leads to the formation of looser globules, allowing for the exchange of the probe molecules between the globules and the external solution.

Chain architectures of various cellulose-based antiscalants on the inhibition of calcium carbonate scale

Two series of cellulose-based antiscalants with different chain architectures, i.e., linear carboxymethyl cellulose (CMC) and branch-shaped carboxymethyl cellulose-graft-poly(acrylic acid) (CMC-g-PAA), were synthesized. The carboxyl groups were distributed on CMC backbone but mainly on the grafted chains of CMC-g-PAA. The addition of CMC and CMC-g-PAA can both increase the surface energy of CaCO3 scale and decrease its crystal nucleation rate, thereby inhibiting CaCO3 scale formation. The structural effects of these cellulose-based antiscalants, especially the chain architectures, on the scale inhibition were investigated in detail. High degree of carboxymethyl substitution caused better inhibition effect of linear CMC. However, CMC-g-PAA with an appropriate content of carboxyl groups but high average number of PAA grafted chains can achieve high inhibition performance. Besides, with similar contents of carboxyl groups, CMC-g-PAA showed much better inhibition performance than CMC due to the distinct multi-dimensional spatial structure of graft copolymer in solution, causing the enhanced chelation and dispersion effects. Characterization of CaCO3 crystal by scanning electron microscopy and X-ray diffraction confirmed that crystal distortion effect obviously existed in CMC but quite minor in CMC-g-PAA. The differences between the scale-inhibition performance of CMC and CMC-g-PAA should be attributed to the different scale-inhibition mechanisms originated in their distinct chain architectures.

The Behavior of Amphiphilic Molecular Brushes with Polyimide Backbone and Poly(methyl methacrylate) and Polystyrene Side Chains in the Vicinity of Θ Point

The behavior of amphiphilic molecular brushes in the vicinity of the Θ point has been studied by the methods of molecular hydrodynamics and optics upon variation of temperature. As objects of investigation, graft copolymers with polyimide main chain and poly(methyl methacrylate) and polystyrene side chains were chosen. The samples studied differed in the backbone and side chain lengths at a similar degree of grafting. The molecular mass of the samples under investigation was varied in a sevenfold range. For comparison, linear poly(methyl methacrylate) and polystyrene have been studied. It has been shown that the behavior of molecular brushes and linear polymers in the vicinity of the Θ point differs significantly. A more rapid gain in intrinsic viscosity of the solutions of graft copolymers in the vicinity of the Θ point is explained by the simultaneous increase in the volume of macromolecules and in their shape asymmetry.

Effect of Side Chains on the Low-Dimensional Self-Assembly of Polyphenylene-Based “Rod–Coil” Graft Copolymers in Solution

We synthesized a series of “rod–coil” graft copolymers containing a laterally expanded poly-p-phenylene (PPP) backbone grafted with nonionic poly(ethylene oxide) (PEO) or ionic poly(acrylic acid) (PAA) side chains (denoted as PPP-g-PEO or PPP-g-PAA). The effect of the side chains on the self-assembly of the graft copolymers in THF–water mixed solvents was investigated. The PPP-g-PEO copolymers exhibited temperature-dependent self-assembly behavior, which is affected by the grafting percentage (GP) and the degree of polymerization (DP) of PEO. At 25 °C, which is higher than the crystallization temperature (Tc) of the PEO chains, PPP-g-PEO self-assembled into ultralong helices with controlled pitches when PN > 6lm/4b, where P represents GP, N denotes DP of PEO, lm expresses the length of a repeating unit in PPP, and b is Kuhn monomer length of a free jointed PEO chain; when PN < 6lm/4b, only nonhelical nanowires were observed. At 10 °C, which is below Tc of PEO, PPP-g-PEO self-assembled into polygonal multi...

Recent advances in the solution self‐assembly of amphiphilic “rod‐coil” copolymers

ABSTRACTSolution self‐assembly of amphiphilic “rod‐coil” copolymers, especially linear block copolymers and graft copolymers (also referred to as polymer brushes), has attracted considerable interest, as replacing one of the blocks of a coil‐coil copolymer with a rigid segment results in distinct self‐assembly features compared with those of the coil‐coil copolymer. The unique interplay between microphase separation of the rod and coil blocks with great geometric disparities can lead to the formation of unusual morphologies that are distinctly different from those known for coil‐coil copolymers. This review presents the recent achievements in the controlled self‐assembly of rod‐coil linear block copolymers and graft copolymers in solution, focusing on copolymer systems containing conjugated polymers, liquid crystalline polymers, polypeptides, and polyisocyanates as the rod segments. The discussions concentrate on the principle of controlling over the morphology of rod‐coil copolymer assemblies, as well as their distinctive optical and optoelectronic properties or biocompatibility and stimuli‐responsiveness, which afford the assemblies great potential as functional materials particularly for optical, optoelectronic and biological applications. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 1459–1477

Green polymer chemistry: One-pot, metal-free synthesis of macromonomer via direct polycondensation of lactic acid and its radical polymerization to graft and comb polymers

A new and simple method of one-pot two-stage poly(lactic acid) (PLA) macromonomer synthesis has been developed. The first stage of the reaction is a direct polycondensation of lactic acid (LA) without a catalyst to PLA, and the second stage is a ring-opening addition of PLA to glycidyl methacrylate (GMA) to afford a PLA macromonomer with a methacryloyl polymerizable group (GMA-Macro). Both reactions are performed consecutively in one pot. This method produced GMA-Macro with high functionality in high yields and thus far seems the simplest and probably the cheapest way to prepare PLA macromonomers. Furthermore, the method is metal-free, offering considerable advantages for biomedical and pharmaceutical applications. GMA-Macro has been shown to be useful for the preparation of PLA graft copolymers in solution or in miniemulsion and of PLA comb polymers in solution. LA is a biobased renewable feedstock. Thus, this method provides a good opportunity to conduct ‘green polymer chemistry’.

Влияние степени прививки на свойства сополимеров на основе метилцеллюлозы и полиакриловой кислоты

&lt;p&gt;In this work, by potentiometric titration the dissociation of the grafted chains of polyacrylic acid in copolymer composition have been investigated. An increase in the content of units of AA in the copolymer leads to a decrease in the values of dissociation constants, that is, the acidic properties are weaken. It was shown that with the extension of the grafted copolymer chains in MC-g-PAA, as well as the enhance the interaction between the basic and graft chains of the copolymer intra- and intermolecular complexes are formed by hydrogen bonding system. Also, by viscometry the effect of the temperature and pH on the rheological properties as well as phase transitions in aqueous solutions of graft copolymers based on polyacrylic acid and methyl cellulose (MC-g-PAA) have been investigated. It was demonstrated that the content of the grafted polyacrylic acid affects to the physicochemical characteristics of the grafted copolymer. Grafting of AA onto a polysaccharide chain allows to create pH-dependent system, resulting in an increase in the solution viscosity of the copolymer with increasing pH.&lt;/p&gt;

Superhydrophobic and oleophobic surfaces obtained by graft copolymerization of perfluoroalkyl ethyl acrylate onto SBR rubber

Abstract Superhydrophobic and oleophobic rubbery coatings were prepared by spraying perfluoroalkyl ethyl acrylate (Zonyl TA-N) grafted styrene butadiene rubber (SBR) solution in toluene after addition of hydrophilic and hydrophobic fumed silica powders onto glass. Grafting onto SBR has been performed by free radical copolymerization in toluene using different Zonyl TA-N feed compositions. Molecular weights of the graft copolymers were determined by GPC and intrinsic viscosity measurements. Thin films of Zonyl TA-N grafted SBR copolymers were prepared by dip coating glass slides into toluene solutions of SBR- g -Zonyl TA-N with varying fluoromonomer contents and their surface free energies were determined by contact angle measurements. The increase in Zonyl TA-N content resulted in a considerable decrease of the total surface free energy of the grafted SBR film. Later, superhydrophobic and oleophobic surfaces were prepared by adding hydrophilic and hydrophobic fumed silica powders into graft copolymer solutions and spraying onto glass. The effect of the Zonyl TA-N content in the graft copolymer, type of silica and its weight concentration in the solution on the water and hexadecane contact angle values, on the surface morphology and mechanical durability of the coatings were investigated. The highest water contact angle of the SBR- g -Zonyl TA-N/SiO 2 hybrid coatings was determined to be 162° and hexadecane contact angle 147° after adjusting the silica type, solids content and fluoroacrylate/SBR composition of the graft copolymer spray solution.

Micellization and demicellization of amphiphilic poly(vinyl acetate)-graft-poly(N-vinyl-pyrrolidone) graft copolymers in the presence of sodium dodecyl sulfate

The micellization of amphiphilic biocompatible poly(vinyl acetate)-graft-poly(N-vinyl-2-pyrrolidone) (PVAc-graft-PNVP) graft copolymers, characterized by a constant PVAc backbone and PNVP side chains of low grafting density as well as of variable chain lengths, reveals the formation of star-like micelles with, at 25°C, a partially “frozen-in” PVAc core and a PNVP corona. The interaction of these graft copolymers with sodium dodecyl sulfate (SDS) was examined on the one side by the so-called “in situ micellization” process consisting in the solubilization of the copolymer in SDS solutions of fixed concentrations and on the other side by the demicellization of preformed copolymer micelles by adding increasing amounts of SDS. In both cases the SDS concentration was kept below its critical micellar concentration (CMC) and the system was investigated by dynamic light scattering (DLS), nuclear magnetic spectroscopy (NMR) and cryogenic-temperature transmission electron microscopy (cryo-TEM). When increasing amounts of SDS are added to a micellar solution of graft copolymer, three regions are observed. At very low surfactant concentrations (region I), a slight decrease in the hydrodynamic radius is observed as a consequence of the copolymer-rich/surfactant complex formation. This complex, which is preferentially formed between SDS hydrocarbon chains and PVAc sequences by hydrophobic interactions, leads to a higher content of the “mobile PVAc”. By a further increase of the SDS concentration (region II), the copolymer micelles start to disintegrate and an abrupt particle size decrease was noticed. A complete demicellization occurs at even higher SDS concentrations where small surfactant-rich/copolymer complexes, as unimers, are predominately present in the system (region III).

Study on the formation of a supramolecular conjugated graft copolymer in solution

The formation in solution of a supramolecular graft copolymer bearing conjugated blocks is demonstrated using diffusion ordered NMR spectroscopy (DOSY). A tailor-made poly(3-(2-ethylhexyl)thiophene) (P3EHT) with a phenol end group is synthesized. For this purpose, the chain-growth mechanism of the polymerization of 2-bromo-5-chloromagnesio-3-alkylthiophenes in the presence of a Ni(dppp) catalyst (dppp = 1,3-bis(triphenylphosphino)propane) is exploited, as it enables the use of functionalized initiators to introduce specific end groups. The so-obtained polythiophene was subsequently mixed in solution with poly(4-vinylpyridine) (P4VP) to enable phenol-pyridine hydrogen bonding. The formation of the supramolecular graft copolymer is studied using DOSY-measurements. Based on the results thereof, the amount of P3EHT attached to the P4VP is calculated and the association constant of the hydrogen bond is estimated. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 804–809

Mechanical Properties of Designed Multicompartment Gels Formed by ABC Graft Copolymers

In the present work, we designed a multicompartment gel by taking advantage of the ABC graft copolymer with a solvophilic A backbone and solvophobic B and C grafts. The mechanical properties of such designed gels were investigated by a combination of dissipative particle dynamics simulation and a nonequilibrium deformation technique. The extensional moduli of multicompartment gels were found to be dependent on polymer concentration and architectural parameters of the graft copolymers (the sequence of graft arms and the position of the graft points). The graft copolymer solutions undergo a sol-gel transition as the polymer concentration increases. This leads to an abrupt increase in the extensional modulus. The studies also revealed that the multicompartment gels of graft copolymers exhibit higher extensional moduli than those of nonmulticompartment gels of graft copolymers and triblock copolymer gels. The position of graft points plays another important role in determining the extensional moduli of the multicompartment gels. The effects of graft positions on the gel modulus were found to be associated with the bridging fraction of graft copolymer chains. The results gained through the present work may provide useful guidance for designing high-performance gels.

Self‐assembly of model graft copolymers of agarose and weak polyelectrolyte‐based amphiphilic diblock copolymers: Controlled drug release and degradation

Polysaccharide-based copolymers are promising biomaterials due to their biocompatibility and biodegradability. For potential biomedical applications the copolymer as a whole and all the degraded species must be biocompatible and easily removable from the system. In this regards, new model pH-responsive seaweed agarose (Agr) grafted with weak polyelectrolyte-based well-defined amphiphilic block copolymers ca. poly[(methyl methacrylate)-b-(2-dimethylamino)ethyl methacrylate)] (PMMA-b-PDMA) were designed and synthesized to study the self-assembly, degradation, and in vitro hydrophobic/hydrophilic drug release behavior. The graft copolymer solutions display extremely low critical micelle concentration (CMC) and form pH responsive stable micelles. The degradation study of the graft copolymer reveals that the entire degraded components are well soluble/dispersible in water due to formation of mixed micelles. The micelles are also strongly adsorbed on the mica surface owing to electrostatic interaction. One application of the graft copolymer micelles is that it can entrap both hydrophilic and poorly water soluble hydrophobic drugs effectively and exhibit slow release kinetics. The release kinetics of both the hydrophilic and poorly water soluble hydrophobic drugs change with pH as well as with the composition of the graft copolymer.

Porous microfibers by the electrospinning of amphiphilic graft copolymer solutions with multi-walled carbon nanotubes

Graft copolymers of polyacrylonitrile-graft-poly(dimethyl siloxane) (PAN-g-PDMS) were synthesized and the solution electrospinning of these materials from dimethylformamide (DMF) was investigated. The amphiphilic nature of the graft copolymers induced phase segregation and self-assembly of the molecules in the electrospinning solution to form a network-like structure. The self-assembly was shown to have a direct effect on the electrospinning parameters affecting the final fiber morphology. The amphiphilic nature of the molecules led to the formation of porous microfibers. Porous fibers are usually obtained via the selective removal of a polymer component in a co-electrospun solution of polymer blends, however, this works presents a novel and direct route for obtaining highly porous electrospun fibers. Multi-walled carbon nanotubes (MWCNT) were also successfully electrospun in the amphiphilic graft copolymer solutions. The inclusion of MWCNT's produces fibers with much smaller diameters, but the porous structure of the fibers is maintained. Excellent dispersion and alignment of the nanotubes along the electrospun fiber axis were obtained. It is shown how the porous electrospun fibers can be used as precursor materials for the production of porous carbon fibers.

Temperature-sensitive hydrogel prepared by graft polymerization of N-isopropylacrylamide onto macroradical Pluronic

A new series of thermo-responsive graft copolymers were prepared via consecutive Pluronic backbone-initiated by t-butylperoxybenzoate with N-isopropylacrylamide (NIPAAm) onto Pluronic by a radical-induced graft polymerization technique. The thermal characterizations of the graft copolymers were investigated by differential scanning calorimetry (DSC). The Pluronic- g-poly(NIPAAm) copolymers exhibited sol-to-gel transitions depending on chain length of the grafted poly(NIPAAm) onto Pluronic. The graft copolymers indicated that the hydrophobic–hydrophilic balance achieved by varying contents of NIPAAm was an important parameter in controlling the transition temperature of the graft copolymers in solution and stability of the resultant gels. The data suggest that graft copolymers may be attractive substrates for tissue engineering and drug delivery applications as the combination of mechanistically independent gelation techniques with regard to gelation kinetics.

Formation of polymer vesicles by amphiphilic fluorosiloxane graft copolymers in solution

Abstract Amphiphilic fluorosiloxane graft copolymers with a poly(dimethylsiloxane) (PDMS) backbone, a hydrophobic fluorosiloxane side-chain and three hydrophilic polyether side-chains were synthesized by hydrosilation reaction in this work. The micellization of amphiphilic graft copolymers in the water/ethanol solvent system was investigated, and vesicles with different size were formed after the self-assembly system was aged for different time.

Synthesis of cellulose-graft-poly(methyl methacrylate) via homogeneous ATRP

Cellulose-graft-poly(methylmethacrylate) (cellulose-g-PMMA) copolymers were prepared by homogeneous atom transfer radical polymerization (ATRP) under mild conditions, in an attempt to develop an efficient way to modify the surface of cellulose. A cellulose macro-initiator was successfully synthesized by direct homogeneous acylation of cellulose with 2-bromopropionyl bromide in a room temperature ionic liquid (RTIL), 1-allyl-3-methylimidazolium chloride ([AMIM]Cl). Copolymers were obtained via ATRP of methyl methacrylate (MMA) with CuBr/penta-methyldiethylenetriamine (PMDETA) as catalyst and N,N-dimethyl-formamide (DMF) as solvent without homopolymer byproduct. The grafting copolymers were characterized by 1H-NMR, 13C-NMR, and FTIR. The grafted PMMA chain was obtained by the hydrolysis of the cellulose backbone and analyzed by GPC and TGA measurements. In addition, the assemblies or aggregates formed by cellulose-g-PMMA copolymers were studied by means of TEM and AFM. The results indicated that the graft polymerization occurred from the cellulose backbone and the obtained copolymers had grafted polymer chains with well-controlled molecular weight and polydispersity; the cellulose graft copolymer in solution could aggregate and self-assemble into sphere-like structures.

In Situ gelling and drug release behavior from novel temperature-sensitive polyaspartamides

Such hydrogels are of par-ticular interest because drugs, proteins and cells can beincorporated easily into polymer solutions prior to adminis-tration and the polymer solution can be injected into thebody without invasive surgical procedures. This method hasbeen developed using thermosensitive polymers or byemploying particular chemical or photochemical reactions.Amphiphilic block or graft copolymer solutions that trans-form from a sol state (flow) to a gel state (non-flow) uponchanges in pH and temperature can be injected subcutane-ously into the target site. In particular, thermo-reversiblehydrogels from amphiphilic block copolymer consisting ofhydrophilic poly(ethylene glycol) (PEG) and hydrophobicaliphatic polyester, such as poly(lactic acid-

PH- and temperature-sensitive PCL-grafted poly(β-amino ester)-poly(ethylene glycol)-poly(β-amino ester) copolymer hydrogels

A series of poly(ɛ-caprolactone)-grafted poly(β-amino ester)-poly(ethylene glycol)-poly(β-amino ester) ((PAE-g-PCL)-PEG-(PAE-g-PCL)) copolymers were designed and synthesized for use in injectable pH- and temperature-sensitive hydrogels. First, PEG diacrylate was synthesized and used as a macroinitiator, and the chain was extended by 4,4 trimethylene dipiperidine (TMDP), 3-amino-1-propanol and diacrylate monomers (1,4-butanediol diacrylate (BDA), and 1,6-hexanediol diacrylate (HDA)) to obtain the triblock copolymers (PAE-PEG-PAE). Poly (ɛ-caprolactone) was then grafted to the pendant OH groups of the resulting PAE-PEG-PAE by ring opening polymerization. The PAE-PEG-PAE and (PAE-g-PCL)-PEG-(PAE-g-PCL) copolymers were characterized by 1H nuclear magnetic resonance (NMR) spectroscopy and gel permeation chromatography. The phase diagram was measured using the tube inverting method. At pH 6.6 or higher, the (PAE-g-PCL)-PEG-(PAE-g-PCL) copolymer solutions (30 wt%) displayed sol-gel-sol transitions with increasing temperature. The viscosity of the graft copolymer solutions was determined as a function of temperature by dynamic mechanical analysis. In addition, after the subcutaneous injection of the polymer solution (30 wt%, pH 6.4) into a rat, a gel formed within a short time, suggesting biomedical applications.

Preparation of cellulose graft poly(methyl methacrylate) copolymers by atom transfer radical polymerization in an ionic liquid

Cellulose graft poly(methyl methacrylate) copolymers were prepared by atom transfer radical polymerization (ATRP) in an ionic liquid. Cellulose chloroacetate, as a macroinitiator, was first synthesized by direct acylation of cellulose with chloroacetyl chloride without any catalysts under mild conditions in an ionic liquid, 1-allyl-3-methylimidazolium chloride (BMIMCl). Then, the macroinitiator was used for the ATRP of MMA mediated by the CuBr and 2,2′-bipyridine (bpy) catalysis system. The copolymerization was carried out in BMIMCl without homopolymer byproduct. The polymers were easily separated from the catalyst when the ionic liquid was used as reaction medium. The grafting copolymers were characterized by means of 1H NMR, AFM and GPC. The results showed that the obtained copolymers had grafted polymer chains with well-controlled molecular weight and polydispersity, and the polymerization was a “living/controlled” system. Further, through AFM observation, it was found that the cellulose graft copolymer in solution could aggregate and self-assembly into sphere-like polymeric structure.