Search

ABSTRACT Amphiphilic hyperbranched copolymer chains made of large hyperbranched poly(acrylic acid) cores grafted with short polystyrene stickers (HB-PAA n- g-PS n + 1) with different n values ( n = 1, 10, 47) were well prepared and confirmed by size exclusion chromatography, Fourier transform infrared spectroscopy and 1H nuclear magnetic resonance. The study on the interchain association behavior of these amphiphilic chains indicates that larger HB-(PAA) n- g-(PS) n + 1 copolymer chains have a less tendency to undergo interchain association. Moreover, the simple vial-inversion and rheological experiments show that the apparent critical gel concentration ( Cg) decreases with n, but no sol-gel transition was observed for triblock PS-PAA-PS even when the concentration is up to 200 g L−1. Further transmission electron microscopy study of the latex particles prepared with HB-(PAA) n- g-(PS) n + 1 as surfactant reveals that the latex particles are spherical and narrowly dispersed; while the measured latex particle number ( Np) indicates the surfactant efficiency of HB-(PAA)47- g-(PS)48 is poorer than that of triblock PS-PAA-PS ( n = 1). Finally, pyrene solubilization measurement shows the solubilization efficiency of HB-(PAA) n- g-(PS) n + 1 copolymers decreases with n, consistent with the previous observed interchain association result. The present study demonstrates that both the chain topology and the styrene weight fraction dominates the final solution properties of amphiphilic HB-(PAA) n- g-(PS) n + 1 chains in aqueous solution. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 128-138 [ABSTRACT FROM AUTHOR]

ABSTRACT Copper-catalyzed azide-alkyne cycloaddition (CuAAC) was used to prepare glycosylated polyethylene (PE)-poly(ethylene glycol) (PEG) amphiphilic block copolymers. The synthetic approach involves preparation of alkyne-terminated PE- b-PEG followed by CuAAC reaction with different azide functionalized sugars. The alkyne-terminated PE- b-PEG was prepared by etherification reaction between hydroxyl-terminated PE- b-PEG ( Mn ∼ 875 g mol−1) and propargyl bromide and azidoethyl glycosides were prepared by glycosylation of 2-azidoethanol. Atmospheric pressure solids analysis probe-mass spectrometry was used as a novel solid state characterization tool to determine the outcome of the CuAAC click reaction and end-capping of PE- b-PEG by the azidoethyl glycoside group. The aqueous solution self-assembly behavior of these amphiphilic glycosylated polymers was explored by TEM and dye solubilization studies. Carbohydrate-bearing spherical aggregates with the ability to solubilize a hydrophobic dye were observed. The potential of these amphiphilic glycosylated polymers to self-assemble via electro-formation into giant carbohydrate-bearing polymersomes was also investigated using confocal fluorescence microscopy. An initial bioactivity study of the carbohydrate-bearing aggregates is furthermore presented. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 5184-5193 [ABSTRACT FROM AUTHOR]

Drugs used for chemotherapy normally carry out adverse, undesired effects. Nanotechnology brings about new horizons to tackle cancer disease with a different strategy. One of the most promising approaches is the use of nanocarriers to transport active drugs. These nanocarriers need to have special properties to avoid immune responses and toxicity, and it is critical to study these effects. Nanocarriers may have different nature, but polypeptide-based copolymers have attracted considerable attention for their biocompatibility, controlled and slow biodegradability as well as low toxicity. Little has been done regarding specific nanocarriers toxicity. In this study, we performed a thorough toxicological study of two different block copolymer nanoparticles (NPs); poly(trimethylene carbonate)- block–poly( l-glutamic acid) (PTMC- b–PGA) and poly(ethylene glycol)- block–poly( γ-benzyl- l-glutamate) (PEG- b–PBLG) with sizes between 113 and 131 nm. Low blood–serum–protein interaction was observed. Moreover, general toxicity assays and other endpoints (apoptosis or necrosis) showed good biocompatibility for both NPs. Reactive oxygen species increased in only two cell lines (HepG2 and TK6) in the presence of PTMC- b–PGA. Cytokine production study showed cytokine induction only in one cell line (A549). We also performed the same assays on human skin organ culture before and after UVB light treatment, with a moderate toxicity after treatment independent of NPs presence or absence. Interleukin 1 induction was also observed due to the combined effect of PEG- b–PBLG and UVB light irradiation. Future in vivo studies for biocompatibility and toxicity will provide more valuable information, but, so far, the findings presented here suggest the possibility of using these two NPs as nanocarriers for nanomedical applications, always taking into account the application procedure and the way in which they are implemented. [ABSTRACT FROM AUTHOR]

ABSTRACT An approach to the synthesis of new regular graft-copolymers polyimide (PI)- graft-polymethacrylic acid is elaborated, including (1) synthesis of multicenter PI macroinitiators, (2) controlled ATRP of tert-butylmethacrylate on the prepared macroinitiators, and (3) protonolysis of tert-butyl ester groups of side chains of the resulting PI- graft-poly( tert-butylmethacrylate). Experimental conditions for attaining complete conversions of the first and the third stages of the process are determined by means of 1H NMR and FTIR-spectroscopy. Polymer products of the first and the second stages of the process, as well as poly( tert-butylmethacrylate) side chains cleaved from the PI- graft-poly( tert-butylmethacrylate) copolymers by complete decomposition of the PI backbone under alkaline hydrolysis conditions, are characterized by GPC. The kinetics of poly( tert-butylmethacrylate) chain growth on a PI macroinitiator under ATRP conditions are studied. The results obtained provide evidence for the controlled character of the ATRP process and the regular structure of the synthesized graft-copolymers. It is shown that PI- g-PMAA PI brushes are significantly more efficient intracellular delivery agents for the potential photosensitizer [tetra(4-fluorophenyl)tetracyanoporhyrazine free base] than are the commonly used PEG-micelles. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 4267-4281 [ABSTRACT FROM AUTHOR]

Abstract: Hypericin (HY) is a naturally-occurring, potent photosensitizer. However, its lipophilicity limits its therapeutic applications. Our attempt is, thus, to develop a biodegradable nanocarrier for hypericin capable of preserving its antibacterial photoactivity. Amphiphilic block copolymers were synthesized to prepare hypericin-laden nanoparticles (HY-NPs). The antimicrobial photoactivity of HY-NPs was assessed; in vitro against biofilm and planktonic cells of methicillin resistant Staphylococcus aureus (MRSA) clinical isolates and in vivo on infected wounds in rats. Nanoparticles of 45nm in diameter ensured higher amounts of reactive oxygen species upon irradiation. HY-NPs demonstrated superior inhibition of biofilm over planktonic cells. In vivo wound healing studies in rats revealed faster healing, better epithelialization, keratinization and development of collagen fibers when HY-NPs were applied. Determination of growth factors and inflammatory mediators in the wound area confirmed superior healing potential of nanoencapsulated hypericin suggesting that hypericin can join the era of antibiotic-free antimicrobial therapy. [Copyright &y& Elsevier]

Highlights: [•] Oligocaprolactone chains are grafted onto starch backbone via CuAAC click chemistry. [•] Azido-functionalized oligocaprolactones are synthesized by functional ROP. [•] Propargylated starch and PCL-g-starch are characterized by NMR and XPS spectroscopy. [•] Swelling behavior of amphiphilic copolymers in interpreted in terms of solubility parameters. [•] The amphiphilic copolymers present the capacity to organize in aggregates in aqueous solutions. [ABSTRACT FROM AUTHOR]

Abstract: Experimental conditions for the synthesis of poly(ε-caprolatone)-graft-poly(vinyl alcohol) (PCL-g-PVA) and poly(l-lactide)-graft-poly(vinyl alcohol) (PLLA-g-PVA) via a PVA/MgH2 macroinitiator were optimized. Heat stability of PVA (99% hydrolyzed) in l-lactide (L-LA) melt was studied by DSC, TGA to lower the reaction temperature and time in order to avoid degradation. Thus, no degradation of copolymers occurred and 13C NMR study showed that l-lactide was incorporated in graft chains as isotactic poly(l-lactide) without racemisation for 140–160°C, up to 25h, L-LA/PVA ratio in the range 3–12. Such synthesis using non-toxic catalyst and reactants in a solvent-free medium can be described as environment-friendly. Amphiphilic behavior of copolymers was studied in aqueous solution according to their chemical structures: critical micelle concentration CMC (0.03–0.5gL−1), average diameter of micelles (80–150nm), surface tension γ CMC (46–63mNm−1), hydrophilic to lipophilic balance HLB (Griffin definition 4–7), and also from cast films: surface energy γ s (36–50mJm−2). This environment-friendly process is suitable for the use of graft PVA copolymers in biomedical area for investigations under micelle applications. [Copyright &y& Elsevier]

Long-subchain hyperbranched polystyrene (lsc-hp PSt) with uniform subchain length was obtained through copper-catalyzed azide-alkyne cycloaddition click chemistry from seesaw macromonomer of PSt having one alkynyl group anchored at the chain centre and two azido group attached to both chain ends [alkynyl-(PSt-N3)2]. After precipitation fraction, different portions of lsc-hp PSt having narrow overall molecular weight distribution were obtained for further grafting with alkynyl-capped poly( N-isopropylacrylamide) (alkynyl-PNIPAM), which was obtained via single-electron transfer living radical polymerization of NIPAM with propargyl 2-bromoisobutyrate as the initiator and grafted onto the peripheral azido groups of lsc-hp PSt via click chemistry. Thus, amphiphilic lsc-hp PSt grafted with PNIPAM chains (lsc-hp PSt- g-PNIPAM) was obtained and would have star-like conformation in tetrahydrofuran (THF). By replacing THF with water, lsc-hp PSt- g-PNIPAM was dissolved at molecular level in aqueous solution due to the hydrophilicity of PNIPAM and exhibited thermal induced shrinkage of PNIPAM arms. The water-insoluble lsc-hp PSt would collapse densely and could be served as a reservoir to absorb hydrophobic chemicals in aqueous solution. The influence of overall molecular weight of lsc-hp PSt on the absorption of pyrene was studied. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013 [ABSTRACT FROM AUTHOR]

A series of carbazole-containing water-dispersible poly(acrylic acid)- b-(9-(4-vinylbenzyl)-9H-carbazole) block copolymers (poly(AA)- b-poly(VBK)) and water-soluble poly(methacrylic acid- ran-(9-(4-vinylbenzyl)-9H-carbazole)) (poly(MAA- ran-VBK)) random copolymers were synthesised in a controlled manner (i.e. low polydispersities $(\overline {M_{{\rm w}} } /\overline {M_{n} } < 1.3)$ by nitroxide-mediated polymerisation (NMP) using an SG1-based alkoxyamine initiator, BlocBuilder. Poly(AA)- b-poly(VBK) block copolymers were most easily accessed by using poly(AA) in its protected form as the macroinitiator for the 9-(4-vinylbenzyl)-9H-carbazole (VBK) block. Controlled polymerisation of MAA was accomplished using an excess of 10 mol.% SG1 relative to BlocBuilder with VBK as controlling co-monomer (initial molar feed content fVBK,0 = 0.03-0.20) in dimethylformamide at 80°C. Poly(MAA- ran-VBK) copolymers with a final VBK molar composition of FVBK < 0.30 resulted in water-soluble copolymers. In addition, as macroinitiators, poly(MAA- ran-VBK)s were sufficiently pseudo-living to reinitiate a second batch of monomer (90 mol.% methyl methacrylate with styrene) in organic solvent and by ab initio, surfactant-free emulsion polymerisation. In both cases, low polydispersity, amphiphilic block copolymers resulted $(\overline {M_{{\rm w}} } /\overline {M_{{\rm n}} } < 1.3)$. © 2012 Canadian Society for Chemical Engineering [ABSTRACT FROM AUTHOR]

Novel amphiphilic graft copolymers of polysulfone (PSU) possessing hydrophilic poly(2-oxazoline) (POx) side chains were synthesized via the ‘grafting from’ method. The cationic ring-opening polymerizations of 2-methyl-2-ozaxoline, 2-ethyl-2-ozaxoline, and 2-propyly-2-ozaxoline were initiated by chloromethylated polysulfone macroinitiator (with 15% benzylchloride content), synthesized by chloromethylation of PSU, in the presence of sodium iodide. The effects of reaction time and type of monomer on the yield, and degree of polymerization were investigated. The obtained polymers were characterized by proton nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, and differential scanning calorimetry analyses. Thin films of graft copolymers were investigated by atomic force microscopy and contact angle measurements. The observed morphologies of thin films were consistent with the amphiphilic nature of the graft copolymers. The films showed temperature dependent surface hydrophobicity due to thermo responsiveness of POx. [ABSTRACT FROM AUTHOR]

Nanosized systems of DOX with antitumor activity on the base of micelle-like particles of amphiphilic thermosensitive copolymers of N -vinylpyrrolidone (VP) with triethylene glycol dimethacrylate (TEGDM), and N -vinylpyrrolidone and methacrylic acid (MAA) with TEGDM were explored. They were investigated in aqueous solutions by electron absorption spectroscopy, dynamic light scattering and cyclic voltammetry. Experimental data and quantum-chemical modeling indicated the formation of a hydrogen bond between oxygen-containing groups of monomer units of the copolymers and H-atoms of OH and NH 2 groups of DOX; the energies and H-bond lengths in the considered structures were calculated. A simulation of TDDFT spectra of DOX and its complexes with the VP and TEGDM units was carried out. Electrochemical studies in PBS have demonstrated that the oxidation of encapsulated DOX appeared to be easier than that of the free one, and its reduction was somewhat more difficult. The cytotoxicity of VP-TEGDM copolymer compositions containing 1, 5 and 15 wt% DOX was studied in vitro on HeLa cells, and the values of IC 50 doses were determined at 24 and 72 h of exposure. The copolymer compositions containing 5 and 15 wt% DOX accumulated actively in cell nuclei and did not cause visual changes in cell morphology.

Low-molecular weight (MW) amphiphilic copolymers have been recently introduced as a powerful tool for the detergent-free isolation of cell membrane proteins. Herein, a screening approach is used to identify a new copolymer type for this application. Via a two-step ATRP/acidolysis procedure, a 3 × 3 matrix of well-defined poly[(butyl methacrylate)-co-(methacrylic acid)] copolymers (denoted BMAA) differing in their MW and ratio of hydrophobic (BMA) and hydrophilic (MAA) units is prepared. Subsequently, using the biologically relevant model (T-cell line Jurkat), two compositions of BMAA copolymers are identified that solubilize cell membranes to an extent comparable to the industry standard, styrene-maleic acid copolymer (SMA), while avoiding the potentially problematic phenyl groups. Surprisingly, while only the lowest-MW variant of the BMA/MAA 2:1 composition is effective, all the copolymers of the BMA/MAA 1:1 composition are found to solubilize the model membranes, including the high-MW variant (MW of 14 000). Importantly, the density gradient ultracentrifugation/sodium dodecyl sulfate-polyacrylamide gel electrophoresis/Western blotting experiments reveal that the BMA/MAA 1:1 copolymers disintegrate the Jurkat membranes differently than SMA, as demonstrated by the different distribution patterns of two tested membrane protein markers. This makes the BMAA copolymers a useful tool for studies on membrane microdomains differing in their composition and resistance to membrane-disintegrating polymers., (© 2022 Wiley-VCH GmbH.)

Previous studies have demonstrated that films of sequence-controlled amphiphilic copolymers display contact angles that depend on microblock size. This suggests that microblock length may provide a means of tuning surface and interfacial properties. In this work, the interfacial rheology of a series of sequence-controlled copolymers, prepared through the addition of bicyclo[4.2.0]oct-1(8)-ene-8-carboxamide (monomer A) and cyclohexene (monomer B) to generate sequences up to 24 monomeric units composed of (A m B n ) i microblocks, where m , n , and i range from 1 to 6. Interfacial rheometry is used to measure the mechanical properties of an air-water interface with these copolymers. As the microblock size increases, the interfacial storage modulus, G' , increases, which may be due to an increase in the size of interfacial hydrophobic domains. Small-angle X-ray scattering shows that the copolymers have a similar conformation in solution, suggesting that any variations in the mechanics of the interface are due to assembly at the interface, and not on solution association or bulk rheological properties. This is the first study demonstrating that microblock size can be used to control interfacial rheology of amphiphilic copolymers. Thus, the results provide a new strategy for controlling the dynamics of fluid interfaces through precision sequence-controlled polymers., Competing Interests: Conflict of Interest The authors declare no conflict of interest.

In this paper, a straightforward method to produce poly(3-hydroxyalkanoate)-based multicompartment micelles (MCMs) is presented. Thiol-ene addition is used to graft sequentially perfluorooctyl chains and poly(ethylene glycol) oligomers onto poly(3-hydroxyoctanoate- co-hydroxyundecenoate) oligomers backbone. Well-defined copolymers are obtained as shown by 1H NMR and size-exclusion chromatography. After nanoprecipitation in water, novel PHA-based MCMs are evidenced by cryo-transmission electron microscopy. Moreover, the cytocompatibility of MCMs is demonstrated in vitro via cell viability assay. [ABSTRACT FROM AUTHOR]

Amphiphilic copolymers, synthesized from poly(ethylene glycols) and various aliphatic and aromatic diacids, which self-assemble into nanomicellar aggregates in aqueous media, were used to develop controlled release (CR) formulations of thiamethoxam (3-(2-chloro-1,3-thiazol-5-ylmethyl)-5-methyl-1,3,5-oxadiazinan-4-ylidene(nitro)amine) using encapsulation technique Formulations were characterised by Infrared (IR) spectroscopy, Dynamic Light Scattering (DLS) and Transmission Electron Microscope (TEM). Encapsulation efficiency, loading capacity and stability after accelerated storage test of the developed formulations were checked. The kinetics of thiamethoxam, released in sandy loam soil from the different formulations was studied. Release from the commercial formulation was faster than the CR formulations. The time taken for release of 50 % of thiamethoxam ranged from 3.56 to 6.07 days for the CR formulations. Although the diffusion exponent (n value) of thiamethoxam in soil ranged from 0.532 to 0.881 in the tested formulations showing non-Fickian transport. These CR formulations may be used in safer, effective and economic crop protection. [ABSTRACT FROM PUBLISHER]

Abstract: Amphiphilic copolymers based on the copolymerization of hydrophilic and hydrophobic moieties offer versatility in various biomedical material applications. Here, a new biocompatible copolymer of dextran-graft-polybutylmethacrylate is synthesized for the coating of metallic endovascular stents. Coating of metallic surfaces is performed and analyzed by X-ray photoelectron spectroscopy, attenuated total reflection Fourier transform infrared spectroscopy, contact angle measurement, atomic force microscopy and scanning electron microscopy before and after deformation corresponding to stent deployment by a balloon catheter. In the conditions described here, the resulting coating is smooth and uniform with neither cracks nor detachment after stent expansion. Interestingly, surfaces coated with the copolymer greatly improve in vitro adhesion and growth of endothelial cells. This copolymer provides new opportunities for implanted biomaterials. [Copyright &y& Elsevier]

Abstract: One of the major industrial uses of lipases is as active agent in bio-based washing formulations. Current methods to improve lipase stability in detergent formulations usually entail a decrease in the enzymatic activity, thus lowering the general performance of the detergent. This work proposes an alternative approach for enzyme stabilization and activity enhancement based on the application of amphiphilic light-harvesting copolymers, called here photozymes. The biopolymer-based chitosan-Rose Bengal and the synthetic poly(SSS0.75–co-VBA0.24–co-VB/hematoporphyrin0.01) photozymes were used as boosting agents in washing formulations containing lipase. Organic stain removal from textiles was improved by 33% at 25°C. This cleaning enhancement was attributed to the increase of lipase activity due to interfacial activation in presence of photozymes, along with prevention of dirt re-deposition on the cleaned surfaces. Although both photozymes improved lipase activity, chitosan-Rose Bengal photozyme performed better at pHs above 9 while at pHs below this value SSS–VBA–VB/HP was the most effective. Dynamic light scattering, zeta-potential measurements, fluorescence spectroscopy and FRET experiments confirmed the pseudomicellar conformation and hosting capacity of the photozymes in aqueous media leading to improved dirt solubilization and emulsification. Moreover, the photocatalytic activity of the photozyme allowed for a de-coloration of the waste washing liquor upon UV irradiation. [Copyright &y& Elsevier]

Novel ABA type amphiphilic copolymers (PCL-APS-PCL) consisting of polycaprolactone (PCL) (A) as hydrophobic block and N, N′-bis (2-hydroxyethyl) methylamine ammonium propane sulfonate (APS) (B) as hydrophilic segment, self-assembled into nanoparticles (NPs) with solvent evaporation method. The sizes and size distributions of NPs were characterized by dynamic light scattering. The morphology of NPs was observed by scanning electron microscopy (SEM). The critical micelle concentration (CMC) was determined by fluorescent probe. The drug loading content (DLC) and the drug release amount were characterized by UV-visible spectrophotometer. The cytotoxicity of the NPs was measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenylte-trazoliumbromide (MTT) assay. It was found that the NPs were spherical in shape with sizes around 100 nm. The CMCs of the copolymers were quite low (×10−4 mg/mL). The DLC decreased with lengthening of hydrophobic PCL block. In vitro drug release experiment demonstrated that the release rate of paclitaxel sped with the decrease of PCL length. MTT results showed that NPs were nontoxic to osteoblast and human epithelial carcinoma (hela) cells. After drug loading, NPs could restrain the growth of hela or even kill hela cells. Therefore, these preliminary studies suggest that the novel PCL-APS-PCL NPs have a great potential application as anticancer drug-delivery carriers. © 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2012. [ABSTRACT FROM AUTHOR]

Polymeric surfaces in contact with blood in vivo are foreign bodies and are quickly isolated from blood by the non-specific defense systems. Nanoparticles (NP) used as drug carriers are normally quickly taken up by phagocytes and sequestered in liver and spleen to which they can deliver drugs. Long-circulating and/or low complement activating core-shell NPs can be obtained from PEO/PEG amphiphilic copolymers forming brush or loops on the surface. Core-shell NPs can also be obtained from polysaccharidic graft or block amphiphilic copolymers. Complement activation by the NPs and protein adsorption both depend on the structure, nature and molecular weight of the polysaccharide chains composing the shell. NPs showing low complement activation can be obtained if the polysaccharide on the surface is long and in a brush configuration. Fragile molecules such as hemoglobin or siRNA can be loaded and protected by appropriate brush shells without modifying the low complement activation properties. [ABSTRACT FROM AUTHOR]

The research topics of our group are in general from the field of physical chemistry of colloidal systems. Within this rather wide layout a large variety of quite different questions and systems are tackled, where the common bridging factor is the aim of understanding the properties of colloidal systems based on their mesoscopic structure and dynamics, which in turn are controlled by their molecular composition. With such an enhanced understanding of the correlation between mesoscopic structure and the macroscopic properties the goal then is to employ this knowledge in order to formulate increasingly complex colloidal system with correspondingly more variable and interesting functionalities. From this general context of investigations, some representative systems and questions that have been studied in recent time by us are covered in this text They comprise the phase behaviour and the structures formed in solutions of surfactants and amphophilic copolymers. Once these static properties are known, we also have a high interest in the dynamic properties and the kinetics of morphological transitions as they are observed under non-equilibrium conditions, since they are frequently encountered in applications. A key property of amphiphilic molecules is their ability to solubilise sparingly soluble compounds thereby forming microemulsions or nanoemulsions, where the ability to form such systems depends strongly on the molecular architecture of the amphiphiles. By turning to polymeric amphiphiles the concept of surfactants and their architecture can be extended largely towards more versatile structures, more complex self-assembly and much larger length and time scales. Another direction is the surfactant assisted formation of nanoparticles or mesoporous inorganic materials. By combining copolymers with other polymers, copolymers, colloids, or surfactants - for instance via electrostatically driven co-assembly - one may then form increasingly complex colloidal aggregates. By doing so one is able to control rheological properties or develop complex delivery systems, whose properties can be tailor-made by appropriate choice of the molecular build-up. This striving towards well controlled complexity achieved by means of self- and co-assembly then leads to increasingly more functional systems and is the key direction for future research activities in our group. [ABSTRACT FROM AUTHOR]

Amphiphilic copolymers, synthesized from poly (ethylene glycols) and various aliphatic diacids, which self assemble into nano-micellar aggregates in aqueous media, were used to develop controlled release (CR) formulations of imidacloprid [1-(6 chloro-3-pyridinyl methyl)-N- nitro imidazolidin-2- ylideneamine] using encapsulation technique. High solubilisation power and low critical micelle concentration (CMC) of these amphiphilic polymers may increase the efficacy of formulations. Formulations were characterised by Infrared (IR) spectroscopy, Dynamic Light Scattering (DLS) and Transmission Electron Microscope (TEM). Encapsulation efficiency, loading capacity and stability after accelerated storage test of the developed formulations were checked. The kinetics of imidacloprid release in water from the different formulations was studied. Release from the commercial formulation was faster than the CR formulations. The diffusion exponent (n value) of imidacloprid, in water ranged from 0.22 to 0.37 in the tested formulations. While the time taken for release of 50 % of imidacloprid ranged from 2.32 to 9.31 days for the CR formulations. The developed CR formulations can be used for efficient pest management in different crops. [ABSTRACT FROM AUTHOR]

Nano-particles with controllable particle size and shape are of great interest in biomedical applications (1). From the standpoint of drug carrier design with wide applicability to a variety of hydrophobic drugs, an effective strategy would be to prepare a simple copolymer having the property to form stable polymeric micelles which can entrap hydrophobic drugs in the core (2). In this study, we have attached saturated and unsaturated long chain acid chlorides to the copolymer of PEG and dimethyl-5-aminoisophthalate via an amide linkage in order to make the copolymers amphiphilic. Further, bioactive compounds like β-carotene, which has considerable double bond unsaturation and curcumin, which has considerable aromatic unsaturation, were encapsulated in these amphiphilic copolymers which successfully demonstrated their drug loading ability. [ABSTRACT FROM AUTHOR]

Amphiphilic triblock copolymers, based on hydrophilic poly(ethylene glycol) (PEG) blocks and hydrophobic poly( l,l-lactide) (PLLA) blocks, were used as the matrix material for the preparation of tetracycline-loaded microspheres. The morphology and thermal properties of the biodegradable microspheres were evaluated. SEM showed the predominance of the spherical shape, however, it was possible to distinguish three patterns: rough or smooth surface or uneven collapsed volume. The FTIR analysis indicated good mechanical stability and structural integrity of the PLLA-PEG-PLLA copolymer's microspheres enclosing tetracycline. By thermal analysis it was possible to see the marginal influence of tetracycline on the glass transition and melting temperatures of the PLLA-PEG-PLLA triblock copolymer, while the results by TG indicated the presence of tetracycline in the inner structure of the microspheres, which thermal decomposition leading to char formation was triggered by the drug's presence. [ABSTRACT FROM AUTHOR]

Dendritic micelles formed from amphiphilic linear-dendritic hybrids based on organic linear poly (ethylene oxide) and inorganic dendritic block containing silicon atoms. The micellar structures of the synthesized copolymers were investigated by TEM images. Thus, two cluster- and flower-like structures were attributed to the first and second generations. The physical parameters of the drug-incorporated carriers, including the drug:carrier ratio, the kinetics of release and the apparent partition constant, were measured. It was observed that the loading efficiency and hydrolytic behavior of the copolymers depend on several factors, such as type of interaction between host and guest molecules, generation of the dendritic copolymers, and pH. [ABSTRACT FROM AUTHOR]

Abstract: Binary complexes of cationic polymers and DNA were used commonly for DNA delivery, whereas, the excess cationic charge of the binary complexes mainly leads to high toxicity and unstability in vivo. In this paper, ternary complexes by coating polyglutamic acid-graft-poly(ethylene glycol)(PGA-g-mPEG) onto binary complexes of polycaprolactone-graft-poly(N,N-dimethylaminoethyl methacrylate) (PCL-g-PDMAEMA) nanoparticles (NPs)/DNA were firstly developed for effective and targeted gene delivery. The coating of PGA-g-mPEG was able to decrease the zeta potential of the nano-sized DNA complexes nearly to electroneutrality without interferring with DNA condensation ability. As a result, the stability, the escape ability from endosomes and the transfection efficiency of the complexes were enhanced. The ternary complexes of PCL-g-PDMAEMA NPs/DNA/PGA-g-mPEG demonstrated lower cytotoxicity in CCK-8 measurements and higher gene transfection efficiency than the binary complexes in vitro. In addition, Lactate dehydrogenase (LDH) assay was performed to quantify the membrane-damaging effects of the complexes, which is consistent with the conclusion of CCK-8 measurement for cytotoxicity assay. The in vivo imaging measurement and histochemical analysis of tumor sessions confirmed that the intravenous administration of the ternary complexes with red fluorescent protein (RFP) as payload led to protein expression in tumor, which was further enhanced by the targeted coating of PGA-g-PEG-folate. [Copyright &y& Elsevier]

Abstract: In this study we present our efforts to homo- and co-polymerize, using group transfer polymerization (GTP), a dialkyl diester of itaconic acid, a naturally-derived unsaturated dicarboxylic acid. The monomer employed, di(n-butyl) itaconate (DBI), did not seem to polymerize by GTP to high conversion, but it displayed the remarkable ability to contribute to the polymer 1–2 units, suggesting that it would make a good end-functionalizing reagent for GTP. This was demonstrated by preparing by GTP hydrophilic homopolymers, and in situ adding to them DBI which is hydrophobic. The thus-obtained amphiphilic end-functionalized copolymers formed in water small micelles, whose aggregation numbers and radii of gyration were characterized using small-angle neutron scattering. [Copyright &y& Elsevier]

The thermal degradation of an amphiphilic block copolymer poly(ethylene)-b-poly(ethylene oxide)-carboxylic acid terminated (PE-b-80%PEO-CHCOOH) and its salt obtained as intermediary product from chemical oxidation of the end group of poly(ethylene)-b-poly(ethylene oxide) (PE-b-80%PEO) has been studied using a thermogravimetric mass spectrometry (TG/MS) coupled system. The isothermal fragmentation of PE-b-80%PEO-CHCOOH showed a more complex fragmentation pattern than PE-b-80%PEO owing to the simultaneous occurrence of the polyether block and the carboxylic end group fragmentations. This led to the appearance of four overlapping ion current peaks of fragments with m/ z 44 and two peaks relative to m/ z 18 at different times by acid-terminated copolymer. For the PE-b-80%PEO copolymer, two ion current peaks associated to m/ z 44 and one large peak relative to m/ z 18 fragments were detected. The intermediary product (PE-b-80%PEO-CHCOO K) showed differences related to the fragmentation behavior. It has more defined ion current signals and presented characteristic peaks attributed to m/ z 43 fragment at the very beginning of the thermal degradation process, which it not detected in the acid copolymer. [ABSTRACT FROM AUTHOR]

Abstract: A group of amphiphilic cationic polymers, methoxy polyethylene glycol-block-(polycaprolactone-graft-poly(2-(dimethylamino)ethyl methacrylate)) (PECD), were synthesized by combining ring-opening polymerization (ROP) and atom transfer radical polymerization (ATRP) methods to form nanoparticles (NPs). The structures of these amphiphilic cationic polymers were characterized by 1H NMR measurement. The PECD NPs have hydrophobic cores covered with hydrophilic PEG and cationic PDMAEMA chains. These self-assembly nanoparticles were characterized by dynamic light scattering (DLS) technique. PECD NPs can effectively condense DNA to form compact complexes of the size 65–160 nm suitable for gene delivery. The in vitro gene transfection studies of HeLa and HepG2 cells show that PECD NPs have better transfection efficiency compared to polyethylenimine (PEI) and Lipofectamine 2000 at low dose (N/P = 5). The cytotoxicity result shows that PECD NPs/DNA complexes at the optimal N/P ratio for transfection have comparable toxicity with PEI and Lipofectamine. These results indicate that PECD NPs have a great potential to be used as efficient polymeric carriers for gene transfection. [ABSTRACT FROM AUTHOR]

Abstract: A new type of copolymer containing two alternating segments, poly-(styrene-alt-maleic anhydride)-co-poly (7-(4-vinylbenzyloxyl)-4-methylcoumarin-alt-maleic anhydride) P(St-alt-MAn)-co-P(VM-alt-MAn)(PSMVM), was prepared. The copolymer self-assembled into nanoparticles with internal microphase structures in water because the hydrophilicity of segment P(VM-alt-MAn) is higher than that of P(St-alt-MAn). The particle size, morphology, ζ potential and surface properties and their dependence on the pH and slat concentrations were studied with a combination of techniques. The nanoparticles of PSMVM showed surface activity and pH sensitivity for producing Pickering oil-in-water emulsions. The emulsion volume increased and the size of oil/water droplet decreased with increasing salt concentration. Furthermore, cross-linked nanoparticles (CLPs) were obtained by photo-dimerization of the pendent coumarin groups in PSMVM under UV irradiation. The emulsions produced by using the CLPs as emulsifiers showed even better stability upon standing. Solid oil-phase droplets were obtained by preparation of CLPs-stabilized Pickering emulsions with an oil phase of styrene containing the initiator AIBN followed by the polymerization of styrene. Thus, the enrichment and aggregation of the CLPs on the emulsion droplets was visible because the solid droplets remained unchanged during the SEM sample preparation. [ABSTRACT FROM AUTHOR]

Abstract: Oil-in-water (O/W) emulsions are typically stabilized using water-soluble surfactants, which anchor to the surface of oil droplets dispersed in an aqueous solution. The structure of the anchored surfactants is often susceptible to physical and chemical stresses because of their highly mobile properties. Here we introduce a new approach to prepare stable silicone oil emulsions under various external stresses using a water-insoluble amphiphilic block copolymer, poly(ethylene oxide)-b-poly(ε-caprolactone) (PEO-b-PCL). Above the melting temperature (around 60°C) of the hydrophobic segment (PCL), PEO-b-PCL can be dissolved in silicone oil. When the polymer/oil mixture is dispersed in water, PEO-b-PCL is irreversibly reorganized into solid nanostructures at the interface of the aqueous/organic phases. The resulting interfacial structures provide a robust physical barrier to the emulsion coarsening processes. Accordingly, the prepared emulsions exhibit excellent structural tolerance against external stresses, including variations in pH, ionic strength, and temperature. [ABSTRACT FROM AUTHOR]

Abstract: Amphiphilic block copolymers are attracting increasing interest in the field of gene therapy, especially for transfection of striated muscles. However, little is known about the parameters affecting their transfection efficiency in vivo. These copolymers can self-assemble as micelles in certain conditions. Since micellization strongly depends on the temperature and ionic content of the preparation medium, the present paper aimed at investigating the influence of these parameters in the context of gene delivery. We first assessed the micellization of pluronic L64 and tetronic 304 at various temperatures in water, saline or Tyrode''s salts solution. Pluronic L64 can form micelles at temperatures above 37 °C in water or at 37 °C in the Tyrode''s salts solution, in the range of concentration investigated. For tetronic 304, CMC was found to be far below the concentrations used to transfer DNA. Pluronic L64 interacted with DNA only in the presence of micelles. Moreover, in vivo evaluation demonstrated that significantly improved transfection efficiency was obtained at 37 °C in Tyrode''s salts solution for pluronic L64 based formulations, compared to 4 °C and 20 °C. Such differences were not recorded with tetronic 304. Finally, optimized formulations of both tetronic 304 and pluronic L64 were able to mediate efficient transfection in dystrophic muscles. [Copyright &y& Elsevier]

Abstract: In this paper three copolymers of polyhydroxyethylaspartamide (PHEA), bearing in the side chains polyethylene glycol (PEG) and/or hexadecylamine (C16) (PHEA-PEG, PHEA-PEG-C16 and PHEA-C16 respectively) have been studied as potential colloidal drug carriers for ocular drug delivery. The physical characterization of all three PHEA derivatives, using the Langmuir trough (LT) and micellar affinity capillary electrophoresis (MACE) techniques allowed to assume that whereas alone PHEA backbone is an inert polymer with respect to the interactions with lipid membranes and drug complexation, when PHEA chains are grafted with long alkyl chains like C16 or in combination C16 chains and hydrophilic chains like PEG, copolymers with lipid membrane interaction ability and drug complexation capability are obtained. In vitro permeability studies performed on primary cultured rabbit conjunctival and corneal epithelia cells, using PHEA-C16 and PHEA-PEG-C16 as micelle carriers for netilmicin sulphate, dexamethasone alcohol and dexamethasone phosphate, demonstrated that in all cases drug loaded PHEA-C16 and PHEA-PEG-C16 micelles provide a drug permeation across ocular epithelia greater than simple drug solutions or suspensions. In particular PHEA-PEG-C16 acts as the best permeability enhancer in our experimental model. In vivo bioavailability studies conducted with PHEA-PEG-C16 micelles loaded with dexamethasone alcohol, confirmed that this system also provides a drug bioavailability greater in comparison with that obtained with water suspension of the same drug after ocular administration to rabbits. [Copyright &y& Elsevier]

Abstract: Striated muscle tissue is an attractive target for gene delivery as it can be easily reached and can express exogenous proteins. However, administration of naked DNA results in low transfection levels, and the design and development of safe and efficient gene delivery systems are thus required. This review is focusing on the characteristics of the striated muscle tissue with regards to features possibly affecting gene transfer, as well as the different soluble polymers that have been evaluated as gene carriers. The described formulations are ranging from polymers displaying a high density of positive charges to non-ionic molecules. Nevertheless, polymers exhibiting few or no positive charges appear to our opinion as the most promising approach to achieve both safe and efficient transfection of the striated muscles. [Copyright &y& Elsevier]

The use of p,α-dimethylstyrene, potentially obtainable from renewable sources, as a substitute for styrene in the synthesis of amphiphilic copolymers is reported in this work. A series of novel poly(p,α-dimethylstyrene- co -maleic anhydride) (SMA) copolymers was synthesized, characterized, and studied as potential polymeric surfactants. After hydrolysis, the copolymers solution properties were compared to the similar and very well-known styrene-maleic acid copolymers. Both series of copolymers were synthesized using reversible addition-fragmentation chain transfer-mediated polymerization (RAFT), and a sample of poly(p,α-dimethylstyrene- co -maleic anhydride) was synthesized via classical free radical polymerization. The synthesized copolymers were studied from the point of view of their solution properties, with particular attention to the influence of the macromolecular and chemical structure on the surface tension of their aqueous solutions. Our results suggest that p,α-dimethylstyrene can be employed in copolymers with maleic anhydride, the resulting material being a valid alternative to SMA copolymers for various applications, such as emulsifiers and dispersants. Furthermore, the DMSMA series seems to be slightly more surface active than SMA. [Display omitted] • The use of a potentially biobased monomer to replace styrene in amphiphilic copolymers is proposed. • Amphiphilic copolymers with various molecular weights can be prepared by RAFT. • The prepared polymers do not form supramolecular aggregates in water. • Solution properties and toxicity are comparable to analogous styrene- co -maleic anhydride polymers. [ABSTRACT FROM AUTHOR]

We synthesized poly(lactide- co-succinimide) (PLS) copolymers with the ratio of lactide to succinimide units of 3:1 and 6.5:1 and studied their elution behavior by size exclusion chromatography with an on-line light-scattering detection. Since the copolymers contain a certain amount of carboxyl groups, they behave as ionomers in N, N-dimethylacetamide (DMAc) and show a typical polyelectrolyte (PE) effect. The PE effect was eliminated by the addition of simple electrolyte like LiBr, H3PO4, or both in DMAc. The efficiency of the additive decreases in the order: LiBr > LiBr + H3PO4 > H3PO4. The ionic strength of the 0.1 M LiBr/DMAc was high enough for the onset of hydrophobic interactions of PLS lactic acid segments intermolecularly as well as with the column packing material. The drawback of the LiBr + H3PO4/DMAc solvent system is a rather high intensity of the system peaks, which are imposed on the right side of the copolymer signal. System peaks strongly influence the determination of number and to a lesser extent the weight average molar masses of PLS copolymers. An addition of only H3PO4 in high enough concentration to DMAc (0.05 and 0.1 M) successfully eliminated the PE effect of the 6.5:1 PLS copolymer. On the contrary, the PE effect of the 3:1 PLS copolymer having higher charge density compared to 6.5:1 PLS copolymer cannot be entirely canceled out in any of the H3PO4/DMAc solutions examined. [ABSTRACT FROM AUTHOR]

Self-assembling micelles, potentially useful as drug delivery systems for ferulic acid (FA), were obtained in aqueous media from amphiphilic α,β-poly(N-2-hydroxyethyl)-dl-aspartamide (PHEA) copolymers bearing at the polyamino acidic backbone both poly(ethyleneglycol) (2000 or 5000 Da) and hexadecylamine (C16) moieties, at a concentration of 7 × 10- 3 and 4 × 10- 3 g/l, respectively, with nanometre size and negative zeta potential. These micelles were able to entrap FA and to release it in a prolonged way in phosphate buffer solution at pH 7.4 and human plasma. These systems were also stable in storage conditions and have no cytotoxic effects on Caco-2, 16 HBE, HuDe and K562 cell lines. Moreover, PHEA-PEG2000-C16 and PHEA-PEG5000-C16 micelles were able to escape from phagocytosis by murine macrophages as a function of the surface PEGylation. [ABSTRACT FROM AUTHOR]

Two chiral amphiphilic diblock copolymers with different relative lengths of the hydrophobic and hydrophilic blocks, poly(6‐O‐p‐vinylbenzyl‐1,2:3,4‐Di‐O‐isopropylidene‐D‐galactopyranose)‐b‐poly(N‐isopropylacrylamide) or poly(VBCPG)‐b‐poly(NIPAAM) and poly(20‐(hydroxymethyl)‐pregna‐1,4‐dien‐3‐one methacrylate)‐b‐poly(N‐isopropylacrylamide) or poly(MAC‐HPD)‐b‐poly(NIPAAM) were synthesized via consecutive reversible addition‐fragmentation chain‐transfer polymerizations of VBCPG or MAC‐HPD and NIPAAM. The chemical structures of these diblock copolymers were characterized by 1H nuclear magnetic resonance spectroscopy. These amphiphilic diblock copolymers could self‐assemble into micelles in aqueous solution, and the morphologies of micelles were investigated by transmission electron microscopy. By comparison with the lower critical solution temperatures (LCST) of poly(NIPAAM) homopolymer in deionized water (32 °C), a higher LCST of the chiral amphiphilic diblock copolymer (poly(VBCPG)‐b‐poly(NIPAAM)) was observed and the LCST increased with the relative length of the poly(VBCPG) block in the copolymer from 35 to 47 °C, respectively. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7690–7701, 2008 [ABSTRACT FROM AUTHOR]

Abstract: Amphiphilic copolymers containing β-cyclodextrin (β-CD) core were synthesized successfully. Synthesis was initiated from tosylated cyclodextrin ((Tosyl)7-β-CD) which is containing two types of functional groups. Hydroxyl functional groups of (Tosyl)7-β-CD were used as initiator for ring opening polymerization of lactide. This step led to star polymers containing tosylated cyclodextrin core and polylactide arms (PLA–(Tosyl)7-β-CD). In the next step, tosyl groups of PLA–(Tosyl)7-β-CD were used as initiator for ring opening polymerization of 2-ethyl-2-oxazoline and amphiphilic copolymers containing cyclodextrin core, PLA and poly(2-ethyl-2-oxazoline) arms (PLA–β-CD–POX) were obtained. Loading of Congo red as guest molecule by amphiphilic copolymers was investigated. The release of guest molecule from chloroform solution of copolymers to water phase was also investigated. [Copyright &y& Elsevier]

Amphiphilic star-block copolymers composed of polystyrene and poly(acrylic acid) were synthesized by iodide-mediated radical polymerization. Firstly, free radical polymerization of styrene was carried out with AIBN as initiator and 1,1,1-trimethyolpropane tri(2-iodoisobutyrate) as chain transfer agent, giving iodine atom ended star-shaped polystyrene with three arm chains, R(polystyrene)3. Secondly, tert-butyl acrylate was polymerization using polystyrene obtained as macro-chain transfer agent, and star-block copolymer, R(polystyrene-b-poly(tert-butyl acrylate))3 with controlled molecular weight was obtained. Finally, amphiphilic star-block copolymer, R(polystyrene-b-poly(acrylic acid))3 was obtained by hydrolysis of R(polystyrene-b-poly(tert-butyl acrylate))3 under acidic condition. [ABSTRACT FROM AUTHOR]

Abstract: Novel amphiphilic graft polyphosphazenes (PNIPAm/EtGly-PPPs) bearing poly (N-isopropylacrylamide) (PNIPAm) as a hydrophilic segment and ethyl glycinate (EtGly) as a hydrophobic group were synthesized via ring-opening polymerization and subsequent substitution reaction. The lower critical solution temperature (LCST) of copolymers was investigated by turbidity method using UV–Vis spectroscopy. Copolymers show their LCSTs in the range of 18.5–33°C, depending on the mole ratio of the substituents. The self-assembly characteristics of copolymers in aqueous solution was studied by using fluorescence technique, dynamic light scattering (DLS), and TEM. The critical association concentration (CAC) of copolymers varied from 0.112 to 0.0309g/L, was related with the mole ratio of PNIPAm to EtGly. The TEM images showed self-assembled nanoparticles with a spherical shape at about 30°C, while network-like aggregates were observed for copolymer with high PNIPAm content at relatively low temperature. The particle size of nanoparticles, depending on copolymer compositions, was in the range of 80–900nm at 25°C. These copolymers may be used as injectable drug carriers for the delivery of hydrophobic compounds. [Copyright &y& Elsevier]

Abstracts: New amorphous amphiphilic triblock copolymers of poly(3-hydroxybutyrate)–poly(ethylene glycol)–poly(3-hydroxybutyrate) (PHB–PEG–PHB) were synthesized using the ring-opening copolymerization of β-butyrolactone monomer. They were characterized by fluorescence, SEM and 1H NMR. These triblock copolymers can form biodegradable nanoparticles with core–shell structure in aqueous solution. Comparing to the poly(ethylene oxide)–PHB—poly(ethylene oxide) (PEO–PHB–PEO) copolymers, these nanoparticles exhibited much smaller critical micelle concentrations and better drug loading properties, which indicated that the nanoparticles were very suitable for delivery carriers of hydrophobic drugs. The drug release profile monitored by fluorescence showed that the release of pyrene from the PHB–PEG–PHB nanoparticles exhibited the second-order exponential decay behavior. The initial biodegradation rate of the PHB–PEG–PHB nanoparticles was related to the enzyme amount, the initial concentrations of nanoparticle dispersions and the PHB block length. The biodegraded products detected by 1H NMR contained 3HB monomer, dimer and minor trimer, which were safe to the body. [Copyright &y& Elsevier]

Amphiphilic poly (MePEG-co-alkyl cyanoacrylate) copolymers have been studied as carriers for stealth nanoparticles. A promising area is nanoparticles prepared using copolymers with both high ratio of PEG blocks and sufficient hydrophobicity. In this study, poly (MePEG cyanoacrylate-co-docosyl cyanoacrylate) copolymer with longer alkyl chains has been synthesized by condensing MePEG cyanoacetate and docosyl cyanoacetate with formaldehyde in the presence of pyrrolidine. The hydrophobicity of the copolymer can be modulated by adjusting the MePEG/docosyl ratio. Characterization of the copolymers has been performed by FTIR, 1H-NMR, and GPC analysis. PEGylated monodisperse nanoparticles were prepared by nanoprecipitation and characterized for particle size, morphology, and zeta potential. Preparation variables such as surfactant concentration in aqueous phase, copolymer concentration, and phase volume ratio influenced particle size. Negative surface zeta potential decreased with increased PEG content in the copolymer, which indicated that nanoparticles prepared with copolymer bearing larger number of PEG moieties provided better shield of the core surface. The newly synthesized copolymer is a potential material to be used to prepare stealth nanoparticles with high PEG density. [ABSTRACT FROM AUTHOR]

Abstract: Biodegradable polymers represent a class of extremely useful materials for many biomedical and pharmaceutical applications, as exemplified by drug delivery systems, which in recent years have taken advantage of (bio)degradable polymeric matrices. However, before being selected for any biomedical application, a biodegradable polymer requires careful investigation of its interactions and compatibility within the human body. To date, polyesters, both natural and synthetic, constitute the most fully developed class of degradable biomaterials. Poly(ε-caprolactone) (PCL) and polylactides (PLAs), recognized as biocompatible and biodegradable polyesters, are very promising for controlled drug delivery devices. Bacterial polyesters and malic acid-based polymers (poly(malic acid), PMLA and derivatives) are poly(β-hydroxyacid)-type polyesters that represent excellent alternatives for temporary therapeutic applications. Although these polyesters can be produced by polycondensation, high molecular weight structures have, until now, been produced almost exclusively by ring-opening polymerization (ROP) of the corresponding cyclic monomers. The ability of aluminum alkoxides (AlR x (OR′)3− x ) and tin(II) bis(2-ethylhexanoate) (Sn(Oct)2) to control the ROP of (di)lactones in terms of molecular parameters has opened the way to a wide range of molecular structures and topologies. Beyond the mechanistic and thermodynamic aspects of ROP of (di)lactones using organometallic compounds, this review is focused on new non-organometallic N-heterocyclic carbenes recently reported as catalysts for the controlled ROP of cyclic esters. Interestingly, the use of these simple organic molecules as catalysts or promoters in asymmetric polymer synthesis has provided organocatalytic alternatives to traditional organometallic reagents. [Copyright &y& Elsevier]

Abstract: Amphiphilic chitooligosaccharide-graft-poly(ε-caprolactone) (COS-g-PCL) copolymers were controllably synthesized using protection/deprotection technique of COS via trimethylsilyl groups and ring-opening polymerization of ε-caprolactone. Their crystalline properties were investigated with differential scanning calorimetry. With the increase of PCL content in graft copolymer, the values of ΔH and X c became enhanced, and T m shifted to higher temperatures. Micellar properties of amphiphilic graft copolymers were studied. Spherical micelles from COS11-g-PCL132 were prepared. However, due to the higher PCL content, the spherical micelles from COS11-g-PCL520 easily confused together so that the complicated network morphology was formed. Interestingly, hierarchical structure was observed in the formed network morphology, as being driven by the crystallization of PCL segments in micelles. Using pyrene as a model compound, the micelles from COS11-g-PCL132 copolymers can be loaded by hydrophobic therapeutic agent, potentially offering an appropriate vehicle for drug delivery. [Copyright &y& Elsevier]

Abstract: The new macroazoinitiators containing poly (propylene glycol), (PPG), with molecular weight 400 and 2000, having hydrophilic character, were synthesized and polymerized with styrene to prepare PS-b-PPG block copolymers. Cast films and e-spun films were prepared and contact angles of these films with water drop were measured to examine hydrophilic/hydrophobic behavior of the copolymers. Each e-spun film with average fiber diameters from 0.25 to 2.20μm was prepared in N,N-dimethylformamide (DMF) under controlled electrospinning process parameters such as polymer concentration, applied voltage and tip-to-collector distance. Scanning electron microscope (SEM) images of the electrospun films were taken to determine the fiber diameters. Surface compositions of the block copolymers were also determined by using an electron spectrometer with MgKα X-rays. NMR, and FT-IR spectroscopic, and GPC measurements were employed to characterize and determine the PPG contents (6–43%). From the results, electrospinning process increased the hydrophilic properties of the block copolymers obtained, compared their cast film forms. Our results suggest that these polymers are favorable in biological applications in cases where high ratio of the surface to volume and hydrophilicity are required simultaneously. Both chemical structure and topology of the films are important in wetting and hydrophobicity. [Copyright &y& Elsevier]

Abstract: Poly(ethylene oxide) monomethylether was functionalized by alkyl chains of various lengths (l=10–19 methylene groups) bearing a polymerizable methacrylate moiety. Each synthesis step on the polymer gives quantitative functionalization rates. The self-assembly of the amphiphilic polymers in water was studied by light scattering for various end-groups. Sterical and polar effects were shown to influence the micellization step. The cores of the micelles formed by PEO-Cl-methacrylate were irreversibly cross-linked by UV irradiation. Star polymers that are stable under dilution in good solvent are obtained after 1-min irradiation. The hydrodynamic radius and the molar mass of the nanoparticles depend on the amount of photoinitiator introduced in the cores. [Copyright &y& Elsevier]

Abstract: Our work focuses on the solubilization of tributylphosphate (TBP), a polar oil, in aqueous solutions of an L64 pluronic ((EO)13–(PO)30–(EO)13). The solubilization capacity of this amphiphilic copolymer highly depends on the temperature. Turbidity measurements show that the increase of the temperature provokes an increase of the hydrophobic character of L64 which favours the TBP solubilization capacity. Two significant temperatures are evidenced; the solubilization minimum temperature (SMT) and the cloud point temperature (CPT). The former is defined as the lowest temperature allowing TBP solubilization in the three-component system (L64–TBP–water). The latter is similar to the cloud point temperature (CPT) defined for the binary systems of water-amphiphile and depends on the copolymer structure, and, more interesting, is directly related to the TBP concentration in the medium. The dependence of CPT with TBP concentration is explained by the change in the hydrophobic character of the (PO)m block and thereby of the whole L64 molecule following solubilization of TBP. A [temperature–composition] diagram allows to delimit monophasic and diphasic domains and to define the optimal temperature for the maximal solubilization of TBP at a given L64 concentration. For a 10wt.% L64 solution, the temperature of 316K is required to solubilize a maximum quantity of TBP. Both turbidity and 1H NMR data suggest the occurrence of two different structures of the three-component system depending on the TBP concentration. During the addition of TBP, the solubilized aggregates turn from swelled aggregates or micelles of amphiphile to nanophase of TBP (nanoemulsion) stabilized by the L64, with an intermediate range of TBP concentration exhibiting a more complex gel-like or precipitated structure. Finally, the analysis of the 1H NMR chemical shifts give relevant information on the different interactions between TBP and L64 and thereby on the location of the TBP molecules in the aggregates. [Copyright &y& Elsevier]

Atom transfer radical polymerization (ATRP) catalyzed by N,N′,N′,N″,N″-pentamethyldiethylenetriamine (PMDETA)/CuBr was performed to synthesize poly (tert-butyl acrylate) (PtBA-Br) with predesigned molecular weight and narrow polydispersity. Using the PtBA-Br as macroinitiator, the PtBA-block-PS copolymer was prepared through ATRP. After terminated bromine atom was converted to end-functional azide group (P(tBA-b-St)-N3), C60 end-capped PtBA-PS block copolymers (P(tBA-b-St)-C60) were synthesized by reacting C60 with P(tBA-b-St)-N3. GPC characterizations showed that C60 was chemically bonded to the end of P(tBA-b-St) chain and the products were mono-substituted. FT-IR, UV-Vis measurements confirmed that hydrolysis of P(tBA-b-St)-C60 resulted in amphiphilic C60 end-capped PAA-PS block copolymers. In additional, the photoconductivity of P(tBA-b-St)-C60 was measured. [Copyright &y& Elsevier]