Novel polyion complex with interpenetrating polymer network of poly(acrylic acid) and partially protected poly(vinylamine) using N-vinylacetamide and N-vinylformamide

Poly(vinylamine), the simplest polycation with primary amines, was applied to interpenetrating polymer networks (IPN) with poly(acrylic acid). N-Vinylformamide (NVF) was employed for amino-protected monomers to control electrostatic balance. pH-responsivities of IPNs varied, depending on the hydrolysis conditions and acrylic acid (AAc) concentration of the second network. Poly(N-vinylacetamide)-co-poly(N-vinylformamide) (4/6, mol/mol) was employed for the first network, subsequently hydrolyzed with 50% amide groups, and the second network was polymerized with 0.25 mol L⁻¹ AAc, extremely shrunken hydrogels with polyion complex were formed at pH 7, showing that the controlled amount of highly active primary amines are available in IPN.     

Functional bioengineering copolymers. II. Synthesis and characterization of amphiphilic poly(N-isopropyl acrylamide-co-maleic anhydride) and its macrobranched derivatives

Radical-initiated copolymerization of N-isopropyl acrylamide (NIPA) with maleic anhydride (MA) and macromolecular reactions of synthesized poly(NIPA-co-MA) with polyethyleneglycol (PEG with a methoxy chain end and molecular weight of 2000 g mol⁻¹) and polyethyleneimine (PEI with molecular weight of 2000 g mol⁻¹) have been studied as a way to obtain new reactive amphiphilic water-soluble polymers potentially useful as carriers for gene delivery. Structure, composition and thermal behaviour of synthesized copolymers and their macrobranched architectures are determined by FTIR, ¹H and ¹³C NMR spectroscopy, elemental (N content) and chemical (acid number) analysis and differential scanning calorimetry, differential thermal and thermal gravimetric methods. It is shown that synthesized copolymers with given composition have low critical solution temperature (LCST) in the range of 30.2-46.4 °C at pH values of 4.0-7.4, which suggest the possibility of their biomedical applications.     

Synthesis of amphiphilic macrocyclic graft copolymer consisting of a poly(ethylene oxide) ring and multi-poly(?-caprolactone) lateral chains

A series of amphiphilic macrocyclic graft copolymers composed of a hydrophilic poly(ethylene oxide) as ring and hydrophobic poly(?-caprolactone) as lateral chains with different grafting lengths and densities of side chains were prepared by a combination of anionic ring-opening polymerization and coordination-insertion ring-opening polymerization. The anionic ring-opening copolymerization of ethylene oxide (EO) and ethoxyethyl glycidyl ether (EEGE) was carried out first using triethylene glycol and diphenylmethyl potassium (DPMK) as co-initiators, and a linear α,ω-dihydroxyl poly(ethylene oxide) with pendant protected hydroxymethyls (l-poly(EO-co-EEGE)) was obtained. The monomer reactivity ratios of these compounds are r_1(EO) = 1.20 ± 0.01 and r_2(EEGE) = 0.76 ± 0.02, respectively. Then the ring closure of l-poly(EO-co-EEGE) was achieved via an ether linkage by reaction with tosyl chloride (TsCl) in the presence of solid KOH. The crude cyclized product containing the linear chain-extended polymer was hydrolyzed in acidic conditions first and then purified by treating with α-CD. The pure cyclic copolymer of EO and glycidol (Gly) with multipendant hydroxymethyls [c-poly(EO-co-Gly)] as the macroinitiator was used further to initiate the ring-opening polymerization of ?-caprolactone (CL), and a series of amphiphilic macrocyclic graft copolymers c-PEO-g-PCL were obtained. The final products and intermediates were characterized by GPC, NMR and MALDI-TOF in detail.     

Gel polymer electrolyte based on poly(acrylonitrile-co-styrene) and a novel organic iodide salt for quasi-solid state dye-sensitized solar cell

A gel polymer electrolyte based on poly(acrylonitrile-co-styrene) as polymer matrix and N-methyl pyridine iodide salt as I⁻ source was prepared. Controlling the concentration of polymer matrix of poly(acrylonitrile-co-styrene) at 17.5 wt.%, mixing the binary organic solvents mixture ethylene carbonate and propylene carbonate with 6:4 (w/w), and the concentration of N-methyl pyridine iodide and iodine with 0.5 and 0.05 M, respectively, the gel polymer electrolyte attains the maximum ionic conductivity (at 30 °C) of 4.63 mS cm⁻¹. Based on the gel polymer electrolyte, a quasi-solid state dye-sensitized solar cell was fabricated and its overall energy conversion efficiency of light-to-electricity of 3.10% was achieved under irradiation of 100 mW cm⁻².     

Synthesis of PAA-g-PNIPAM well-defined graft polymer by sequential RAFT and SET-LRP and its application in preparing size-controlled super-paramagnetic Fe3O4 nanoparticles as a stabilizer

A series of well-defined double hydrophilic graft copolymers, poly(acrylic acid)-g-poly(N-isopropylacrylamide) (PAA-g-PNIPAM), was employed as a novel water-soluble coating for constructing superparamagnetic iron oxide nanoparticles. The copolymer was synthesized via a three-step procedure: firstly, a well-defined hydrophobic PtBA-based backbone, poly(tert-butyl 2-((2-chloropropanoyloxy)-methyl)acrylate)-co-poly(tert-butyl acrylate), (PtBCPMA₁₉-co-PtBA₁₈), was prepared through RAFT copolymerization of a new trifunctional acrylic monomer, tert-butyl 2-((2-chloropropanoyloxy)methyl)acrylate and tert-butyl acrylate; secondly, taking this backbone as a macroinitiator to initiate SET-LRP of N-isopropylacrylamide resulted in well-defined (poly(tert-butyl 2-((2-chloropropanoyloxy)methyl)-acrylate)-co-poly(tert-butyl acrylate))-g-poly(N-isopropylacrylamide) ((PtBCPMA-co-PtBA)-g-PNIPAM) amphiphilic graft copolymers with relatively narrow polydispersities (M_w/M_n ≤ 1.31); thirdly, handling (PtBCPMA-co-PtBA)-g-PNIPAM in acidic conditions afforded PAA-g-PNIPAM graft copolymers. The resulting PAA-g-PNIPAM copolymers were directly utilized as a polymeric stabilizer in the preparation of superparamagnetic Fe₃O₄ nanoparticles. The particle size can be readily tuned in the range of 12.1–23.2 nm by varying the amount of PAA-g-PNIPAM copolymer or the length of PNIPAM side chain. Besides, the structure and properties of prepared Fe₃O₄/polymer nanocomposites were characterized by XRD, FT-IR, TGA, TEM, and magnetic measurement in detail.     

Synthesis of thermoresponsive poly(N-isopropylmethacrylamide) and poly(acrylic acid) block copolymers via post-functionalization of poly(N-methacryloxysuccinimide)

Polymers exhibiting a thermoresponsive, lower critical solution temperature (LCST) phase transition have proven to be useful for many applications as “smart” or “intelligent” materials. A series of poly(N-isopropylmethacrylamide) (PNIPMAM) polymer, poly(N-isopropylmethacrylamide)-b-poly(acrylic acid) (PNIPMAM-b-PAA) diblock, and poly(acrylic acid)-b-poly(N-isopropylmethacrylamide)-b-poly(acrylic acid) (PAA-b-PNIPMAM-b-AA) triblock copolymer samples were synthesized via ATRP. A facile post-functionalization route was developed that uses an activated ester functionality to convert poly(N-methacryloxysuccinimide) (PMASI) blocks to LCST capable polyacrylamide, while poly(t-butyl acrylate) (PtBA) blocks were converted to water-soluble poly(acrylic acid) (PAA). The post-functionalization was monitored via ¹H NMR and ATR-FTIR. The aqueous solution properties were explored and the PNIPMAM polymers were shown to have a LCST phase transition varying from 35 to 60 °C. The ability to synthesize block copolymers that are thermoresponsive and water-soluble will be of great benefit for broader applications in drug delivery, bioengineering, and nanotechnology.     

Synthesis of electrically conducting copolymers of aniline with o/m-amino benzoic acid by an inverse emulsion pathway

Copolymers of aniline and ortho/meta-amino benzoic acid were synthesized by chemical polymerization using an inverse emulsion pathway. The copolymers are soluble in organic solvents, and the solubility increases with the amino benzoic acid content in the feed. The reaction conditions were optimized with emphasis on high yield and relatively good conductivity (2.5×10⁻¹ S cm⁻¹). The copolymers were characterized by a number of techniques including UV-vis, FT-IR, FT-Raman, EPR and NMR spectroscopy, thermal analysis, SEM and conductivity. The influence of the carboxylic acid group ring substituent on the copolymers is investigated. The spectral studies reveal that the amino benzoic acid groups restrict the conjugation along the polymer chain. The SEM micrographs of the copolymers reveal regions of amorphous and crystalline domain. Thermal studies indicate a marginally higher thermal stability for poly(aniline-co-m-amino benzoic acid) compared to poly(aniline-co-o-amino benzoic acid).     

Double-responsive core-shell-corona micelles from self-assembly of diblock copolymer of poly(t-butyl acrylate-co-acrylic acid)-b-poly(N-isopropylacrylamide)

Self-assembly of poly(t-butyl acrylate-co-acrylic acid)-b-poly(N-isopropylacrylamide) [P(tBA-co-AA)-b-PNIPAM], which was obtained from part hydrolysis of PtBA-b-PNIPAM synthesized by sequential atom transfer radical polymerization (ATRP) was studied. Thermo- and pH-responsive core-shell-corona (CSC) micelles with different structures were formed from (PtBA-co-PAA)-b-PNIPAM in aqueous solution. At pH 5.8 and 25 °C, the block copolymer self-assembled into spherical core-shell micelles with hydrophobic PtBA segments as the core, hydrophilic PAA/PNIPAM segments as the mixed shell. Increasing temperatures, core-shell micelles converted into CSC micelles with PtBA as the core, collapsed PNIPAM as the shell and soluble PAA as the corona. Moreover, decreasing pH at 25 °C, PAA chains collapsed onto the core resulting in CSC micelles with PtBA as the core, PAA as the shell and PNIPAM as the corona.     

Preparation and structure characterization of hairy nanoparticles consisting of hydrophobic core and thermosensitive hairs

Structural characterization of hairy nanoparticles consisting of poly(styrene-co-glycidyl methacrylate) (St/GMA) core and poly(NIPA-co-vinylimidazole) (NIPA/VIm) hair has been carried out by dynamic light scattering. The hairy molecules were introduced by surface graft-polymerization of a mixture of NIPA and VIm monomers to the St/GMA core particles with the hydrodynamic radius R_H of 135±10 nm. The R_H of St/GMA-core-NIPA/VIm-hair particles was R_H=360±20 nm at 20 °C, which gradually decreased to 285±10 nm by heating to 33.0 °C, and then underwent a sharp decrease to 175±10 nm by further heating to 33.8 °C. The final value went to 159±10 nm at 36 °C. This decrease in R_H is due to the shrinking transition of NIPA/VIm chain by hydrophobic association. The degree of shrinking of the hairy particles is compared with that of bulk NIPA gels from the viewpoint of geometrical constraints.     

pH- and thermo-multi-responsive fluorescent micelles from block copolymers via reversible addition fragmentation chain transfer (RAFT) polymerization

Well-defined pH- and thermo- multi-responsive fluorescent micelles based on the self-assembly of diblock copolymers poly[(N-isopropyl-acrylamide-co-N-vinylcarbazole)-b-2-(dimethylamino)ethyl acrylate], (PNIPAAM-co-PNVC)-b-PDMAEA, are described. The diblock copolymers are prepared via the reversible addition fragmentation chain transfer (RAFT) copolymerization of N-isopropyl-acrylamide (NIPAAM) and N-vinylcarbazole (NVC) followed by chain extension in presence of 2-(dimethylamino)ethyl acrylate) (DMAEA). The micelles are formed in aqueous solutions in a wide range of temperature (25-60 °C), and their sizes increase from 40 to 65 nm when varying pH from basic to acidic. The cross-linking of the PDMAEA-containing shell with 1,2-bis(2-iodoethoxy)ethane (BIEE) results in spherical soft nanoparticles which size is increased by 20-25% when compared to the micelles. The presence of NVC in concentrations as low as 4% in the core of the micelles allow the nanoparticles to be tagged by fluorescence, making them well suited for therapeutic applications.     

Preparation of star copolymers with three arms of poly(ethylene oxide-co-glycidol)-graft-polystyrene and investigation of their aggregation in water

The star graft copolymers with three arms composed of poly(ethylene oxide) (PEO) as main chain and polystyrene (PS) as side chains were prepared by sequential anionic ring-opening copolymerization of ethylene oxide and ethoxyethyl glycidyl ether (EEGE), and then atom transfer radical polymerization (ATRP) of styrene. The anionic ring-opening copolymerization of EO and EEGE was carried out using 2-ethyl-2-hydroxymethyl-1,3-propanediol as trifunctional initiator and diphenylmethyl potassium (DPMK) as deprotonating agent. The resulting three-arm star copolymer [poly(EO-co-EEGE)]₃ could be easily hydrolyzed to unmask the pendant hydroxyl groups without affecting the PEO chains. The switch from the first to the second mechanism was completed by the reaction of the multi-pendant hydroxyl groups of three-arm PEO chain with 2-bromoisobutyryl bromide. The obtained poly(ethylene oxide-co-2-bromoisobutyryloxyglycidyl ether), [poly(EO-co-BiBGE)]₃, was used as macroinitiators to initiate the polymerization of styrene in bulk at 90 °C by ATRP. The final products and intermediates were characterized by NMR, SEC and IR in detail. The amphiphilic star graft copolymers synthesized can form micelles in water. The critical micelle concentration (cmc) determined by fluorescence spectra was about 5 × 10⁻⁷ g/mL. Sphere micelles were observed by transmission electron microscopy (TEM) at low copolymer concentration (6 × 10⁻⁵ g/mL), but the micelle shape became irregular when the copolymer concentration increased to 6 × 10⁻⁴ g/mL.     

Living and block polymerization of α-olefins using a Ni(II)-α-diimine catalyst containing OSiPh2Bu groups

A new siloxy-substituted α-diimine compound and its corresponding Ni(II) complex, {bis[N,N′-(4-tert-butyl-diphenylsiloxy-2,6-dimethylphenyl)imino]acenaphthene}dibromonickel (6), were successfully synthesized and the molecular structure of 6 characterized by X-ray crystallography. The precatalyst 6 activated by methylaluminoxane (MAO) or diethylaluminum chloride (DEAC) was tested in the polymerization of ethylene, showed to be highly active (e.g. 2.2×10⁷ and 1.8×10⁷ g polymer (mol Ni.h.bar)⁻¹, respectively) and led to a branched polyethylene (ca. 35-55 branches/1000 C). The catalyst system 6/methylaluminoxane (MAO) catalyzes, at −11 °C, living polymerization of propylene, to a polypropylene showing a syndiotactic-rich microstructure (P_r=0.74). 1-Hexene was also successfully polymerized via a living process, both at −11 and +16 °C. The ¹³C NMR spectra of the poly(1-hexene)s obtained at room temperature show a microstructure almost exclusively composed by n-butyl and methyl branches, the latter being present in a much higher number. Diblock polypropylene-block-poly(1-hexene) and triblock poly(1-hexene)-block-poly(propylene-ran-1-hexene)-block-poly(1-hexene) copolymers have also been synthesized and characterized by GPC/SEC, DSC and NMR.     

Novel chemically cross-linked solid state electrolyte for dye-sensitized solar cells

Poly(vinylpyridine-co-ethylene glycol methyl ether methacrylate) (P(VP-co-MEOMA)) and α,ω-diiodo poly(ethylene oxide-co-propylene oxide) (I[(EO)_0.8-co-(PO)_0.2]_yI) were synthesized and used as chemically cross-linked precursors of the electrolyte for dye-sensitized solar cells. Meanwhile, α-iodo poly(ethylene oxide-co-propylene oxide) methyl ether (CH₃O[(EO)_0.8-co-(PO)_0.2]_xI) was synthesized and added into the electrolyte as an internal plasticizer. Novel polymer electrolyte resulting from chemically cross-linked precursors was obtained by the quaterisation at 90 °C for 30 min. The characteristics for this kind of electrolyte were investigated by means of ionic conductivity, thermogravimetric and photocurrent-voltage. The ambient ionic conductivity was significantly enhanced to 2.3 × 10⁻⁴ S cm⁻¹ after introducing plasticizer, modified-ionic liquid. The weight loss of the solid state electrolyte at 200 °C was 1.8%, and its decomposition temperature was 287 °C. Solid state dye-sensitized solar cell based on chemically cross-linked electrolyte presented an overall conversion efficiency of 2.35% under AM1.5 irradiation (100 mW cm⁻²). The as-fabricated device maintained 88% of its initial performance at room temperature even without sealing for 30 days, showing a good stability.     

Synthesis and characterization of amphiphilic functional polyesters by ring-opening polymerization and click reaction

During this work we have prepared novel amphiphilic graft-block (PαN₃CL-g-alkyne)-b-PCL functional polyesters, comprising poly(α-azido-ε-caprolactone-graft-alkyne) (PαN₃CL-g-alkyne) as the hydrophilic segment and poly(ε-caprolactone) (PCL) as the hydrophobic segment, by ring-opening polymerization of ε-caprolactone (ε-CL) with hydroxyl-terminated macroinitiator PαClCL, substituting pendent chloride with sodium azide. The copolymers were subsequently used for grafting of 2-propynyl-terminal alkyne moieties by the Cu(I)-catalyzed Huisgen’s 1,3-dipolar cycloaddition, thus producing a “click” reaction. ¹H NMR, FT-IR, GPC, and differential scanning calorimetry (DSC) examined the characteristics of the copolymers. Grafting of PMEs or PMPEGs onto the PαN₃CL-b-PCL caused these amphiphilic copolymers to self-assemble into micelles in the aqueous phase. Fluorescence, dynamic light scattering (DLS) and transmission electron microscopy (TEM) then examined these micelles. The critical micelle concentration (CMC) ranged from 8.2 mg L⁻¹ to 39.8 mg L⁻¹ at 25 °C and the average micelle size ranged from 140 to 230 nm. The hydrophilicity and length of the hydrophilic segment influenced micelle stability. The current study describes the drug entrapment efficiency and drug loading content of the micelles, dependent on the composition of graft-block polymers. The results from in vitro cell viability assays indicated that (PαN₃CL-g-alkyne)-b-PCL shows low cytotoxicity.     

Investigation of water diffusion in poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) by generalized two-dimensional correlation ATR-FTIR spectroscopy

Water diffusion process in biodegradable poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx, HHx = 12 mol%) was investigated by generalized 2D correlation time-resolved ATR-FTIR spectroscopy based on the analysis of v(OH) stretching and δ(OH) bending bands of water as well as v(CO) and v(C-O-C) stretching bands of PHBHHx. Three states of water were figured out during water diffusion process. They are bulk water, bound water and free water. The water diffusion mechanism was suggested as: water molecules firstly diffuse into the micro-voids in bulk water form or are dispersed on the surface in free water form, and then penetrate into the polymer matrix in hydrogen bound water with the hydrophilic groups of PHBHHx. Moreover, water molecules diffuse into the loose amorphous phase and then into compact crystalline phase. Water diffusion coefficient in PHBHHx was thus evaluated as 7.8 ± 0.7 × 10⁻⁸ cm² s⁻¹ for the PHBHHx with crystallinity of 16.2 ± 0.3% at 293 K.     

Preparation of a microporous polymer electrolyte based on poly(vinyl chloride)/poly(acrylonitrile-butyl acrylate) blend for Li-ion batteries

Poly(acrylonitrile-co-butyl acrylate) (P(AN-co-BuA))/poly(vinyl chloride) (PVC) blend-based gel polymer electrolyte (BGPE) was prepared for lithium-ion batteries. The P(AN-co-BuA)/PVC BGPE consists of an electrolyte-rich phase, which is mainly composed of P(AN-co-BuA) and liquid electrolyte, acting as a conducting channel and a PVC-rich phase that provides mechanical strength. The dual phase was just simply developed by the difference of miscibility properties in solvent, PC, between P(AN-co-BuA) and PVC. The mechanical strength of this new blend electrolyte was found to be much higher, with a fracture stress as high as 29 MPa in dry membrane and 21 MPa in gel state, than that of a previously reported P(AN-co-BuA)-based gel polymer electrolyte. The blended gel polymer electrolyte showed ionic conductivity of higher than 1.5 × 10⁻³ S cm⁻¹ and electrochemical stability up to at least 4.8 V. The results showed that the as-prepared gel polymer electrolytes were promising materials for lithium-ion batteries.     

Controllable synthesis of poly(N-vinylpyrrolidone) and its block copolymers by atom transfer radical polymerization

At room temperature atom transfer radical polymerization (ATRP) of N-vinylpyrrolidone (NVP) was carried out using 5,5,7,12,12,14-hexamethyl-1,4,8,11-tetra-azacyclo-tetradecane (Me₆Cyclam) as ligand in 1,4-dioxane/isopropanol mixture. Methyl 2-chloropropionate (MCP) and copper(I) chloride were used as initiator and catalyst, respectively. The polymerization of NVP via ATRP could be mediated by the addition of CuCl₂. The resultant poly(N-vinylpyrrolidone) (PNVP) has high conversion of up to 65% in 3 h, a controlled molecular weight close to the theoretical values and narrow molecular weight distribution between 1.2 and 1.3. The living nature of the ATRP for NVP was confirmed by the experiments of PNVP chain extension. With PNVP-Cl as macroinitiator and N-methacryloyl-N′-(α-naphthyl)thiourea (MANTU) as a hydrophobic monomer, novel fluorescent amphiphilic copolymers poly(N-vinylpyrrolidone)-b-poly(N-methacryloyl-N′-(α-naphthyl)thiourea) (PNVP-b-PMANTU) were synthesized by ATRP. PNVP-b-PMANTU copolymers were characterized by ¹H NMR, GPC-MALLS and fluorescence measurements. The results revealed that PNVP-b-PMANTU presented a blocky architecture.     

Synthesis of biodegradable poly(trans-4-hydroxy-N-benzyloxycarbonyl-l-proline)-block-poly(ε-caprolactone) copolymers and micellar characterizations

A series of novel types of diblock poly(trans-4-hydroxy-N-benzyloxycarbonyl-l-proline)-block-poly(ε-caprolactone) (PHpr10-b-PCL) copolymers were synthesized by ring-opening polymerization from macroinitiator poly(trans-4-hydroxy-N-benzyloxycarbonyl-l-proline) (PHpr10) and ε-caprolactone (ε-CL) in the presence of organocatalyst dl-lactic acid (dl-LA). The M_n of the copolymers increased from 3370 to 19,040 g mol⁻¹ with the molar ratio (10-100) of ε-CL to PHpr10. These products were characterized by differential scanning calorimetry (DSC), ¹H NMR, and gel permeation chromatography. According to DSC, the glass-transition temperature (T_g) of the diblock copolymers depend on the molar ratio of monomer/initiator that were added. The hydrolytic degradation behavior of PHpr-b-PCLs was evaluated from weight-loss measurements and the change of M_n and M_w/M_n. With higher PCL contents resulted in a slower weight loss, while having a higher molecular weight loss percentage. Their micellar characteristics in an aqueous phase were investigated by fluorescence spectroscopy, transmission electron microscopy (TEM), and dynamic light scattering (DLS). The block copolymers formed micelles in the aqueous phase with critical micelle concentrations (CMCs) in the range of 1.33-4.22 mg L⁻¹. The micelles exhibited a spindly shape and showed a narrow monodisperse size distribution. The obtained micelles have a relatively high drug-loading of about 26% when the feed weight ratio of amitriptyline hydrochloride (AM) to polymer was 1/1. An increase of molecular weight and hydrophobic components in copolymers produced a higher CMC value and greater loading efficiencies were observed.     

Cellular uptake of tailored copolymer synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization

The tailored copolymer poly(methoxy-PEG acrylate-co-N-hydroxysuccinimide-co-fluorescein diacetate 5-maleimide) (P1) and block copolymer poly(N-isopropylacrylamide)-b-poly(methoxy-PEG acrylate-co-N-hydroxysuccinimide-co-fluorescein diacetate 5-maleimide) (P2) were synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization, which were both water-soluble, fluorescent and containing active group N-hydroxysuccinimide (NHS). Due to the temperature-sensitive poly(N-isopropylacrylamide) unit, the latter copolymer P2 formed nanoparticles at 37 °C in aqueous medium. Both P1 and P2 were taken up by cultured human umbilical vein endothelial cells (HUVECs) and localized mainly in the cytoplasm, which could subsequently be detected by confocal laser scanning microscopy (CLSM).     

Preparation of core cross-linked micelles using a photo-cross-linking agent

A new method for preparing polymeric, core cross-linked (CCL) micelles has been developed using a bifunctional photo-cross-linking agent of di(4-hydroxyl benzophenone) dodecanedioate (BPD). An amphiphilic diblock copolymer of poly(ethylene glycol)-b-poly(2-hydroxyethyl methacrylate-co-methyl methacrylate) (PEG-b-P(HEMA-co-MMA)) was synthesized via atom-transfer radical polymerization (ATRP) using a PEG macroinitiator at 85 °C. The core domains of the PEG-b-P(HEMA-co-MMA) micelles containing BPD in aqueous solution were successfully photo-cross-linked by UV irradiation for only 30 min. The HEMA units incorporated in the hydrophobic block of PEG-b-P(HEMA-co-MMA) donated labile hydrogens to excited-state BP groups in BPD, and they were subsequently cross-linked by BPD through radical-radical combination. A sufficient degree of cross-linking was obtained at an equivalent ratio of the BP groups to the HEMA units.