Application of thermo-responsive poly(methyl vinyl ether) containing copolymers in combination with ultrasonic treatment for pigment surface modification in pigment dispersions

The process of surface modification of hydrophobic organic (copper phthalocyanine (CuPc)) as well as hydrophilic inorganic pigments (titanium dioxide) in aqueous dispersions by employing tailor-made thermo-responsive copolymers and the colloidal stability have been studied as a function of temperature. The pigment surface modification is achieved by conventional adsorption and by thermoprecipitation of amphiphilic methyl vinyl ether (MVE) containing block and graft copolymers, exhibiting a lower critical solution temperature (LCST), with poly(isobutyl vinyl ether) blocks and poly(ethylene oxide) side chains, respectively. The effect of mechanical treatment of the pigment dispersion by ultrasonic power alone or in combination with the LCST property was investigated. The course of the pigment surface coating process was followed by the electrokinetic sonic amplitude (ESA) method. The temperature-controlled sorption of PMVE-g-PEO graft copolymers on both inorganic and organic pigment surfaces was investigated. It was found that ultrasonic treatment together with LCST thermoprecipitation is a promising method for the surface modification of pigments with regard to dispersion stability.     

Synthesis and micellization of a new amphiphilic star-shaped poly(D,L-lactide)/polyphosphoester block copolymer

A new amphiphilic 4-arm star-shaped poly(D,L-lactide)/poly(ethyl ethylene phosphate) (ssPLA-b-PEEP) block copolymer was synthesized by ring-opening polymerization of ethyl ethylene phosphate (EEP) with hydroxyl terminated 4-arm star-shaped poly(D,L-lactide) (ssPLA) as a macroinitiator, which was prepared by ring-opening polymerization of D,L-lactide (LA) initiated by pentaerythrite using stannous octoate as catalyst. The structures of the block copolymers were confirmed by IR, ¹H-NMR and GPC analysis. Fluorescence measurements were applied to determine the critical micelle concentration (CMC) of the copolymer micelle solutions. The diameter and the distribution of micelles were characterized by dynamic light scattering (DLS) and the shape was perceived by transmission electron microscopy (TEM). The results indicated those copolymers formed nano-micelles in aqueous solution with hydrophobic poly(D,L-lactide) core and hydrophilic poly(ethyl ethylene phosphate) shell. The CMC of the copolymer solutions increased with the increments of the proportion of PEEP segments. TEM images demonstrated that all micelles were spherical.     

Novel non-ionic block copolymers tailored for interactions with phospholipids

The bulk of literature on phospholipid membrane interactions with non-ionic amphiphilic block copolymers deals with ABA triblock copolymers of poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide). This is partially the result of their commercial availability. In recent years novel block copolymers have been synthesized and their interactions with phospholipids structured as Langmuir monolayers, liposomes, bilayer lipid membranes, tethered bilayers, and living cells have been studied. This review describes some new block copolymers with potential to interact with phospholipids. There is a tremendous progress in synthesis of amphiphilic block copolymers triggered by new controlled polymerization techniques as atom transfer radical polymerization or nitroxide mediated polymerization and by the possibility to ‘click’ preformed blocks together using quantitative reactions of functional endgroups. A special focus is given to novel water soluble amphiphilic triblock copolymers of poly(glycerol monomethacrylate)-b-poly(propylene oxide)-b-poly(glycerol monomethacrylate) and their interactions with phosphatidylcholine lipids. Also block copolymers containing hydrophobic blocks with perfluoroalkyl groups are discussed since they are special in a sense that their fluorophilic blocks are neither hydrophilic nor oleophilic as this is the case for conventional amphiphilic block copolymers. Experimental methods to study block copolymer–phospholipid interactions are summarized and selected results based on special experimental techniques such as isothermal titration calorimetry, infrared reflection absorption spectroscopy and ion conductance are presented. This work is intended to convey a better quantitative understanding of amphiphilic block copolymers used for in vitro and in vivo experiments in medicine and pharmacy.     

Synthesis and self-association in aqueous media of poly(ethylene oxide)/poly(ethyl glycidyl carbamate) amphiphilic block copolymers

New temperature sensitive AB, ABA, and BAB amphiphilic block copolymers consisting of hydrophilic poly(ethylene oxide) and hydrophobic poly(ethyl glycidyl carbamate) blocks were synthesized by anionic polymerization followed by chemical modification reactions. The self-association of the block copolymers in aqueous media was studied by UV-vis spectroscopy and dynamic and static light scattering. The obtained block copolymers spontaneously form micelles in aqueous media. The critical micellization concentration varied from 0.5 to 4 g/L depending on the copolymer architecture and composition. The influence of the temperature upon the self-association of the block copolymers was investigated. The increase of temperature did not affect the value of the critical micellization concentration, but led to the formation of better defined micelles with narrow size distribution.     

Synthesis, characterization and properties of functional star and dendritic block copolymers of ethylene oxide and glycidol with oligoglycidol branching units

Well-defined, four-arm star block copolymers of ethylene oxide and glycidol were prepared via controlled anionic polymerization using protected glycidol. The length of the poly(ethylene oxide) block was varied from DP = 10 to 50, while the length of the short polyglycidol block remained nearly constant, at DP = 4-6. Star block copolymers with hydroxyl groups at the ends of the arms after conversion to the corresponding alkoxides were used as multifunctional macroinitiators for the sequential polymerization of ethylene oxide and protected glycidol. After deprotection, the branched block copolymers of ethylene oxide and glycidol had narrow molar mass distributions and multiple hydroxyl groups (up to 200) at the peripheries. The structure and functionality were determined using size exclusion chromatography with a light scattering detector and nuclear magnetic resonance spectroscopy. The thermal properties of the synthesized copolymers were also investigated, as well as the hydrophilic dye uptake to the hydrophobic phase containing copolymers.     

Preparation of poly[dl-lactide-co-glycolide]-based microspheres containing protein by use of amphiphilic diblock copolymers of depsipeptide and lactide having ionic pendant groups as biodegradable surfactants by W/O/W emulsion method

To develop the preparative method for poly(dl-lactide-co-glycolide)-based microspheres containing proteins, we prepared microspheres from mixture of poly(dl-lactide-co-glycolide) and polydepsipeptide-block-poly(dl-lactide) having cationic or anionic pendant groups. Since the latter amphiphilic copolymers consisting of hydrophobic poly(dl-lactide) segment and hydrophilic polydepsipeptide segment with amino or carboxyl groups could be converted to cationic or anionic block copolymers, they could act as biodegradable surfactants on the preparation of poly(dl-lactide-co-glycolide)-based microspheres by water-in-oil-in-water emulsion method. The amphiphilic block copolymers were established to stabilize primary emulsions on the preparation of microspheres by scanning electron microscopy. We investigated the effects of the addition of the block copolymers on the entrapment efficiency of protein, the release behavior of protein from microspheres and the stability of protein.     

Surface properties of polymer films including multiblock copolymer

B(AB)_n multiblock copolymers of which the A block and the B block are hydrophobic and hydrophilic, respectively, were blended into crosslinkable coating compositions for preparing a hydrophilic surface, and compared with the graft copolymers including A and B as the pendant groups. The main constituent of A was polydimethyl-siloxane and that of B was poly(ethylene oxide). While the block copolymer slightly increased the hydrophobicity of the surface, it quickly became hydrophilic on contact with water. On the contrary, the graft copolymer increased the hydrophobicity even after its contact with water. Elementary analysis with ESCA demonstrated that both the silicon atoms and ether groups were concentrated on the very top of the surface in the films including the block copolymers but only silicon atoms were concentrated on the film surface which included the graft copolymers. In spite of their propensity to remain in the bulk due to their high surface energy, hydrophilic poly(ethylene oxide) moieties in the block copolymers migrated onto the near surface accompanying the movement of the hydrophobic polydimethyl-siloxane. because their mobility would be restricted by the bonding of both sides. Inclusion of the block copolymers significantly improved soil resistance. The advantage of the block copolymers as a surface modifier was further developed as an adhesion promoter. The introduction of a larger amount of the hydroxyl group into the hydrophilic block was effective for this purpose. This was discussed with respect to the change in the γ_p parameter.     

Preparation,morphology and sonication time dependence of silver nanoparticles in amphiphilic block copolymers of PEO with polystyrene or PMMA

Composite materials comprising arrays of silver nanoparticles in amphiphilic copolymers have been prepared by sonochemically enhanced borohydride reduction of precursor silver nitrate (AgNO₃). The precursor was incorporated into the cores of polymeric micelles formed from block copolymers of polystyrene (PS) or poly(methyl methacrylate) (PMMA) with poly(ethylene oxide) (PEO). The copolymers were synthesised with varying hydrophobic block lengths from a PEO macroinitiator by atom transfer radical polymerization (ATRP). UV/visible spectroscopy was used to confirm the formation of elemental silver and the effect of sonication time on the appearance of the silver nanoparticles was determined. The growth was faster than when gold nanoparticles are formed in comparable block copolymers. Nanoparticles formed in copolymers with PMMA blocks were more stable to agglomeration than when polystyrene was used. Electron microscopy revealed the morphology of the nanocomposites which confirmed that both block copolymers are vehicles for the formation of well-defined films containing nanoparticulate silver. However, AgNP formation shows some significant differences from previous reports of gold NP containing materials formed under similar conditions.     

Synthesis and morphology transformation of amphiphilic diblock polyurethane copolymers in aqueous solution

Amphiphilic block copolymers possess both hydrophobic and hydrophilic properties and can form versatile micellar structures in aqueous solution. The aim of the research presented was to prepare a series of non‐ionic amphiphilic diblock polyurethane copolymers (PUn) based on isophorone diisocyanate, monoallyl‐end‐capped poly(ethylene oxide) and poly(propylene oxide) (PPO), followed by an investigation of their micellization properties and morphology transformation in aqueous solution. The PUn samples were synthesized by condensation polymerization. These polyurethanes exhibit surface tension as low as 33.7–37.0 mN m^?1. There is an obvious decrease in critical micelle concentration as the hydrophobic PPO molecular weight increases. According to transmission electron microscopy, the morphology of aggregates of the copolymers can be tuned by varying the concentration in aqueous solution rather than organic solvent. For example, for PU7, large compound micelles are produced instead of vesicles. For PU17, the concentration can be used to control the size and thickness of vesicles. Vesicle size increases from 60 to 500 nm and vesicle thickness from 40 to 60 nm with concentration ranging from 0.003 to 0.03 wt%. The study shows that the copolymers in aqueous solution have excellent surface activities. In addition, they can self‐assemble into large compound micelles or vesicles at certain concentrations. Moreover, the synthesis method described allows one to obtain a desired morphology of aggregates by adjusting the composition of hydrophilic and hydrophobic segments, which provides a novel and simple way to obtain particles on the nanometer scale. Copyright © 2010 Society of Chemical Industry     

Poly(allyl glycidyl ether)‐block‐poly(ethylene oxide): A novel promising polymeric intermediate for the preparation of micellar drug delivery systems

Novel diblock copolymers designed for the preparation of micellar drug delivery systems, consisting of hydrophobic poly(allyl glycidyl ether) (PAGE) and hydrophilic poly(ethylene oxide) (PEO), were prepared, and their self‐assembly into micellar structures was studied. Copolymers differing in the length of the polymer blocks were purified and characterized. These amphiphilic copolymers with narrow molecular weight distributions were prepared through the anionic polymerization of allyl glycidyl ether with PEO monomethyl ether sodium salt as the macroinitiator. The PAGE–PEO copolymer readily formed small micelles with narrow size distributions via simple dissolution in water. The addition of pendant double bonds to the hydrophobic part of the chain was intended for further covalent modifications. Catalytic hydrogenation, the radical crosslinking of the micelle core, and the addition of thiol to double bonds of the copolymer were examples of such modifications that were proved to proceed with a quantitative yield for this copolymer. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 201–211, 2005     

Vesicular and micellar self‐assembly of stimuli‐responsive poly(N‐isopropyl acrylamide‐b‐9‐anthracene methyl methacrylate) amphiphilic diblock copolymers

Dually responsive amphiphilic diblock copolymers consisting of hydrophilic poly(N‐isopropyl acrylamide) [poly(NIPAAm)] and hydrophobic poly(9‐anthracene methyl methacrylate) were synthesized by reversible addition fragmentation chain‐transfer (RAFT) polymerization with 3‐(benzyl sulfanyl thiocarbonyl sulfanyl) propionic acid as a chain‐transfer agent. In the first step, the poly(NIPAAm) chain was grown to make a macro‐RAFT agent, and in the second step, the chain was extended by hydrophobic 9‐anthryl methyl methacrylate to yield amphiphilic poly(N‐isopropyl acrylamide‐b‐9‐anthracene methyl methacrylate) block copolymers. The formation of copolymers with three different hydrophobic block lengths and a fixed hydrophilic block was confirmed from their molecular weights. The self‐assembly of these copolymers was studied through the determination of the lower critical solution temperature and critical micelle concentration of the copolymers in aqueous solution. The self‐assembled block copolymers displayed vesicular morphology in the case of the small hydrophobic chain, but the morphology gradually turned into a micellar type when the hydrophobic chain length was increased. The variations in the length and chemical composition of the blocks allowed the tuning of the block copolymer responsiveness toward both the pH and temperature. The resulting self‐assembled structures underwent thermally induced and pH‐induced morphological transitions from vesicles to micelles and vice versa in aqueous solution. These dually responsive amphiphilic diblock copolymers have potential applications in the encapsulation of both hydrophobic and hydrophilic drug molecules, as evidenced from the dye encapsulation studies. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46474.     

Novel amphiphilic poly(ester‐urethane)s based on poly[(R)‐3‐hydroxyalkanoate]: synthesis,biocompatibility and aggregation in aqueous solution

BACKGROUND: The aim of this work was to develop polyhydroxyalkanoates (PHAs) for blood contact applications, and to study their self‐assembly behavior in aqueous solution when the PHAs are incorporated with hydrophilic segments. To do this, poly(ester‐urethane) (PU) multiblock copolymers were prepared from hydroxyl‐terminated poly(ethylene glycol) (PEG) and hydroxylated poly[(R)‐3‐hydroxyalkanoate] (PHA‐diol) using 1,6‐hexamethylene diisocyanate as a coupling reagent. The PEG segment functions as a soft, hydrophilic and crystalline portion and the poly[(R)‐3‐hydroxybutyrate] segment behaves as a hard, hydrophobic and crystalline portion. In another series of PU multiblock copolymers, crystalline PEG and completely amorphous poly[((R)‐3‐hydroxybutyrate)‐co‐(4‐hydroxybutyrate)] behaved as hydrophobic and hydrophilic segments, respectively. RESULTS: The formation of a PU series of block copolymers was confirmed by NMR, gel permeation chromatography and infrared analyses. The thermal properties showed enhanced thermal stability with semi‐crystalline morphology via incorporation of PEG. Interestingly, the changes of the hydrophilic/hydrophobic ratio led to different formations in oil‐in‐water emulsion and surface patterning behavior when cast into films. Blood compatibility was also increased with increasing PEG content compared with PHA‐only polymers. CONCLUSION: For the first time, PHA‐based PU block copolymers have been investigated in terms of their blood compatibility and aggregation behavior in aqueous solution. Novel amphiphilic materials with good biocompatibility for possible blood contact applications with hydrogel properties were obtained. Copyright © 2008 Society of Chemical Industry     

Synthesis of poly(fluorinated styrene)‐block‐poly(ethylene oxide) amphiphilic copolymers via atom transfer radical polymerization: potential application as paper coating materials

BACKGROUND: The surface of a substrate which comprises a fibrous material is brought into contact with a type of amphiphilic block copolymer which comprises hydrophilic/hydrophobic polymeric blocks. These amphiphilic copolymers have been synthesized by atom transfer radical polymerization (ATRP) technique. The atom transfer radical polymerization of poly(2,3,4,5,6‐pentafluorostyrene)‐block‐poly(ethylene oxide) (PFS‐b‐PEO) copolymers (di‐ and triblock structures) with various ranges of PEO molecular weights was initiated by a PEO chloro‐telechelic macroinitiator. The polymerization, carried out in bulk and catalysed by copper(I) chloride in the presence of 2,2′‐bipyridine ligand, led to A–B–A amphiphilic triblock and A–B amphiphilic diblock structures. RESULTS: With most of the macroinitiators, the living nature of the polymerizations led to block copolymers with narrow molecular weight distributions (1.09 < M_w/M_n < 1.33) and well‐controlled molecular structures. These block copolymers turned out to be water‐soluble through adjustment of the PEO block content (>90 wt%). Of all the block copolymers synthesized, PFS‐b‐PEO(10k)‐b‐PFS containing 10 wt% PFS was found to retard water absorption considerably. CONCLUSION: The printability of paper treated with the copolymers was evaluated with contact angle measurements and felt pen tests. The adsorption of such copolymers at the solid/liquid interface is relevant to the wetting and spreading of liquids on hydrophobic/hydrophilic surfaces. Copyright © 2009 Society of Chemical Industry     

A new synthetic approach to asymmetric amphiphilic ABA′ block copolymers by ATRP and click reactions

Well‐defined asymmetric amphiphilic ABA′ block copolymers composed of poly(ethylene oxide) monomethylene ether (MPEO) with different molecular weights as A or A′ block and poly(styrene) (PS) as B block were synthesized by the combination of atom transfer radical polymerization (ATRP) and click reactions. First, bromine‐terminated diblock copolymer poly(ethylene oxide) monomethylene ether‐block‐poly(styrene) (MPEO‐PS‐Br) was prepared by ATRP of styrene initiated with macroinitiator MPEO‐Br, which was prepared from the esterification of MPEO and 2‐bromoisobutyryl bromide. Then, the azido‐terminated diblock copolymers MPEO‐PS‐N₃ were prepared through the bromine substitution reaction with sodium azide. Propargyl‐terminated MPEO with a different molecular weight was prepared under the basic condition from propargyl alcohol and p‐toluenesulfonyl‐terminated MPEO, which was prepared through the esterification of MPEO and p‐toluenesulfochloride using pyridine as solvent. Asymmetric amphiphilic ABA′ block copolymers, with a wide range of number–average molecular weights from 1.92 × 10⁴ to 2.47 × 10⁴ and a narrow polydispersity from 1.03 to 1.05, were synthesized via a click reaction of the azido‐terminated diblock copolymers and the propargyl‐terminated MPEO in the presence of CuBr and 1,1,4,7,7‐pentamethyldiethylenetriamine (PMDETA) catalyst system. The structures of these ABA′ block copolymers and corresponding precursors were characterized by NMR, IR, and GPC. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Pluronic嵌段共聚物胶束化行为及其胶束增溶

两亲性质的Pluronic嵌段共聚物在合适条件下能自发形成内核很大的稳定胶束 ,其胶束化行为复杂 ,初步的研究深化了对两亲分子自组织机理的认识。实验发现这类胶束具有很强的增溶油溶性物质的能力 ,由于这些分子单体和胶束化行为的特点 ,可望利用这类嵌段共聚物实现在增溶应用场合中的突破。综述Pluronic嵌段共聚物的胶束化行为和胶束增溶规律的当前研究进展     

Synthesis and pH-dependent micellization of 2-(diisopropylamino)ethyl methacrylate based amphiphilic diblock copolymers via RAFT polymerization

The polymerization of 2-(diisopropylamino)ethyl methacrylate (DPA) by RAFT mechanism in the presence of 4-cyanopentanoic acid dithiobenzoate in 1,4-dioxane was studied. The DPA homopolymer was employed as a macro chain transfer agent to synthesize pH-sensitive amphiphilic block copolymers using poly(ethylene glycol) methyl ether methacrylate (PEGMA) as the hydrophilic block. ¹H NMR and GPC measurements confirmed the successful synthesis of these copolymers. Potentiometric titrations and fluorescence experiments proved that the copolymers underwent a sharp transition from unimers to micelles at a pH of ∼6.7 in phosphate buffered saline solutions. It was found that the hydrophilic/hydrophobic balance of these block copolymers had no apparent effect on their pH-induced micellization behaviors. The DLS investigation revealed that the micelles have a mean hydrodynamic diameter below 60 nm with a narrow size distribution.     

Synthesis and physicochemical characterization of amphiphilic block copolymers bearing acid-sensitive orthoester linkage as the drug carrier

Amphiphilic block copolymers bearing an acid-sensitive orthoester linkage, composed of hydrophilic poly(ethylene glycol) (PEG) and hydrophobic poly(γ-benzyl L-glutamate) (PBLG), were prepared as the carrier capable of selectively releasing the hydrophobic drug at the mildly acidic condition. Diblock copolymers with various lengths of PBLG were synthesized via ring opening polymerization of benzyl glutamate NCA in the presence of the acid-labile PEG as a macroinitiator. Owing to their amphiphilicities, the copolymers formed spherical micelles in aqueous conditions, and their particle sizes (22-106 nm in diameter) were dependent on the block length of PBLG. These nanoparticles were stable in the physiological buffer (pH 7.4), whereas they were readily decomposed under the acidic condition. In particular, the block copolymer with a smaller hydrophobic portion was rapidly disassembled under the acidic condition. Doxorubicin (DOX), chosen as the model anti-cancer drug, was effectively encapsulated into the hydrophobic core of the micelles using the solvent casting method. The loading efficiency depended on the hydrophobic block length of the copolymer; i.e., the longer hydrophobic block allowed for loading of larger amounts of the drug. In vitro release studies demonstrated that DOX was slowly released from the pH-sensitive micelles in the physiological buffer (pH 7.4), whereas the release rate of DOX significantly increased under the acidic condition (pH 5.0). From the in vitro cytotoxicity test, it was found that DOX-loaded pH-sensitive micelles showed higher toxicity to SCC7 cancer cells than DOX-loaded micelles without the orthoester linker. These results suggest that the amphiphilic block copolymer bearing the orthoester linkage is useful for pH-triggered delivery of the hydrophobic drug.     

Enhanced therapeutic efficacy of clotrimazole by delivery through poly(ethylene oxide)-block-poly(ε-caprolactone) copolymer-based micelles

Amphiphilic block copolymers have been the subject of great scientific interests due to their applications in various fields including nano drug delivery. Three amphiphilic block copolymers based on poly(ε-caprolactone) as a hydrophobic segment and methoxy poly(ethylene oxide) ( as a hydrophilic part were synthesized by the ring-opening polymerization of ε-caprolactone using MeO-PEO_5K as macroinitiator by varying initial feed ratios. The synthesized polymers were further explored for their drug delivery potential using clotrimazole as model hydrophobic drug. Drug-loaded micelles were characterized for shape, size, drug encapsulation efficiency, in vitro release, and thermal stability using atomic force microscope, zetasizer, UV–visible spectrophotometry, FTIR, differential scanning calorimetry, and thermogravimetric analysis. Clotrimazole loaded in micelles were also investigated for its antifungal activity through an in vitro assay and scanning electron microscopy. The antifungal activity of drug increased significantly by delivering through polymeric micelles. Current study provides insight into different factors that can be maneuvered to achieve a variety of desired properties of micelles for improved therapeutic efficacy of drugs like clotrimazole. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47769.     

Synthesis and properties of block poly(ether‐ester)s based on poly(ethylene oxide) and various hydrophobic segments

To obtain biodegradable amphiphilic block polymers for biomedical applications, a series of poly(ether‐ester)s based on poly(ethylene oxide) and various hydrophobic/hydrophilic segment ratios were synthesized by the solution polymerization technique. The polyesters were characterized using ¹H NMR spectroscopy, elemental analysis, gel permeation chromatography, differential scanning calorimetry, thermogravimetric analysis and compression stress–strain measurements. The composition of the poly(ether‐ester)s agreed with the feed ratio. A study of the degree of phase segregation in the polymers evidenced that microphase mixing increases with the presence in the hydrophobic segments of polar groups able to establish interactions with the poly(ethylene oxide). This phase mixing increased the thermal stability of the acidic poly(ether‐ester)s. Nanospheres for drug delivery with an average diameter of 50 nm were obtained by employing the acidic poly(ether‐ester) showing less microphase segregation, while a scaffold structure with a homogeneous and highly interconnected porosity and an average pore size of approximately 15 µm for tissue engineering was prepared using the more hydrophobic copolymer not possessing functional groups. Compression mechanical measurements carried out on the scaffold showed that the more hydrophobic copolymer was suitable for tissue engineering applications. In order to obtain polymers employable both in drug delivery and in tissue engineering a series of block poly(ether‐ester)s showing various phase segregations were synthesized by varying the hydrophobic/hydrophilic segment ratio. Copyright © 2010 Society of Chemical Industry     

Synthesis and characterization of star-shaped block copolymer of poly-(?-caprolactone) and poly(ethyl ethylene phosphate) as drug carrier

A series of novel 4-arm biodegradable star block copolymers of poly(?-caprolactone) and poly(ethyl ethylene phosphate) were synthesized via ring-opening polymerization of 2-ethoxy-2-oxo-1,3,2-dioxaphospholane using hydroxyl terminated 4-arm star-shaped poly(?-caprolactone) and stannous octoate co-initiation system. Gel permeation chromatography (GPC), NMR and FT-IR were used to demonstrate the structure and analyze their compositions. The self-assembly behavior of these star-shaped copolymers in aqueous solution was studied by ¹H NMR and fluorescence technique, and the results indicated those copolymers formed nanoparticles in aqueous solution with hydrophobic poly(?-caprolactone) core and hydrophilic poly(ethyl ethylene phosphate) shell. The critical micelle concentration was relative to the length of poly(?-caprolactone) and poly(ethyl ethylene phosphate) block. Paclitaxel was encapsulated in the micelles and the release behavior demonstrated that a longer hydrophobic block resulted in slightly slower release rate from the micelles. These copolymer micelles were biocompatible and potential as drug-delivery vehicles for pharmaceutical application.