Synthesis of poly(di[methylamine]ethyl methacrylate)‐b‐poly(cyclohexyl methacrylate)‐b‐poly(di[methylamine]ethyl methacrylate) amphiphilic triblock copolymers by ATRP: Condensed‐phase and solution properties

The synthesis of amphiphilic triblock copolymers, poly(di[methylamine]ethyl methacrylate)‐b‐poly(cyclohexyl methacrylate)‐b‐poly(di[methylamine]ethyl methacrylate) PDMAE‐b‐PCH‐b‐PDMAE, has been performed by atom transfer radical polymerisation. Those have been obtained in a well‐controlled manner in terms of molecular weight and polydispersity index. The triblock copolymer characterisation has been made in condensed state and in solution. The existence of microphase separation has been confirmed by differential scanning calorimetry. However, the domains of both inner and outer blocks seem not to be ordered for one another from small‐angle X‐ray scattering (SAXS) measurements using synchrotron radiation. The micelle formation in dilute methanol solutions has been confirmed for all triblock copolymers by dynamic light scattering analyses. The size of these micelles has been demonstrated to be dependent on the molecular weight. Similar observations have been made in concentrate methanol solutions by using SAXS experiments, pointed also out that an increment of the intermicelle interactions is produced as the concentration increases. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 85–92, 2008     

Block copolymer mediated synthesis of amphiphilic gold nanoparticles in water and an aqueous tetrahydrofuran medium: An approach for the preparation of polymer–gold nanocomposites

The synthesis of polymer‐matrix‐compatible amphiphilic gold (Au) nanoparticles with well‐defined triblock polymer poly[2‐(N,N‐dimethylamino)ethyl methacrylate]‐b‐poly(methyl methacrylate)‐b‐poly[2‐(N,N‐dimethylamino)ethyl methacrylate] and diblock polymers poly(methyl methacrylate)‐b‐poly[2‐(N,N‐dimethylamino)ethyl methacrylate], polystyrene‐b‐poly[2‐(N,N‐dimethylamino)ethyl methacrylate], and poly(t‐butyl methacrylate)‐b‐poly[2‐(N,N‐dimethylamino)ethyl methacrylate] in water and in aqueous tetrahydrofuran (tetrahydrofuran/H₂O = 20:1 v/v) at room temperature is reported. All these amphiphilic block copolymers were synthesized with atom transfer radical polymerization. The variations of the position of the plasmon resonance band and the core diameter of such block copolymer functionalized Au particles with the variation of the surface functionality, solvent, and molecular weight of the hydrophobic and hydrophilic parts of the block copolymers were systematically studied. Different types of polymer–Au nanocomposite films [poly(methyl methacrylate)–Au, poly(t‐butyl methacrylate)–Au, polystyrene–Au, poly(vinyl alcohol)–Au, and poly(vinyl pyrrolidone)–Au] were prepared through the blending of appropriate functionalized Au nanoparticles with the respective polymer matrices {e.g., blending poly[2‐(N,N‐dimethylamino)ethyl methacrylate]‐b‐poly(methyl methacrylate)‐b‐poly[2‐(N,N‐dimethylamino)ethyl methacrylate‐stabilized Au with the poly(methyl methacrylate)matrix only}. The compatibility of specific block copolymer modified Au nanoparticles with a specific homopolymer matrix was determined by a combination of ultraviolet–visible spectroscopy, transmission electron microscopy, and differential scanning calorimetry analyses. The facile formation of polymer–Au nanocomposites with a specific block copolymer stabilized Au particle was attributed to the good compatibility of block copolymer coated Au particles with a specific polymer matrix. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1841–1854, 2006     

Biocompatible and pH‐responsive triblock copolymer mPEG‐b‐PCL‐b‐PDMAEMA: Synthesis,self‐assembly,and application

A series of well‐defined amphiphilic triblock copolymers [polyethylene glycol monomethyl ether]‐block‐poly(ε‐caprolactone)‐block‐poly[2‐(dimethylamino)ethyl methacrylate] (mPEG‐b‐PCL‐b‐PDMAEMA or abbreviated as mPEG‐b‐PCL‐b‐PDMA) were prepared by a combination of ring‐opening polymerization and atom transfer radical polymerization. The chemical structures and compositions of these copolymers have been characterized by Fourier transform infrared spectroscopy, ¹H NMR, and thermogravimetric analysis. The molecular weights of the triblock copolymers were obtained by calculating from ¹H NMR spectra and gel permeation chromatography measurements. Subsequently, the self‐assembly behavior of these copolymers was investigated by fluorescence probe method and transmission electron microscopy, which indicated that these amphiphilic triblock copolymers possess distinct pH‐dependent critical aggregation concentrations and can self‐assemble into micelles or vesicles in PBS buffer solution, depending on the length of PDMA in the copolymer. Agarose gel retardation assays demonstrated that these cationic nanoparticles can effectively condense plasmid DNA. Cell toxicity tests indicated that these triblock copolymers displayed lower cytotoxicity than that of branched polyethylenimine with molecular weight of 25 kDa. In addition, in vitro release of Naproxen from these nanoparticles in pH buffer solutions was conducted, demonstrating that higher PCL content would result in the higher drug loading content and lower release rate. These biodegradable and biocompatible cationic copolymers have potential applications in drug and gene delivery. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1079–1091, 2010     

Syntheses and characterizations of poly[2‐(dimethylamino)ethyl methacrylate]–poly(propylene oxide)–poly[2‐(dimethylamino)ethyl methacrylate] ABA triblock copolymers

A novel, near‐monodisperse, well‐defined ABA triblock copolymer, poly[2‐(dimethylamino)ethyl methacrylate]‐b‐poly(propylene oxide)‐b‐poly[2‐(dimethylamino)ethyl methacrylate], was synthesized via oxyanion‐initiated polymerization. The initiator was a telechelic‐type potassium alcoholate prepared from poly(propylene glycol) and KH in dry tetrahydrofuran. The copolymers produced were characterized by Fourier transform infrared, ¹H NMR, and gel permeation chromatography (GPC). GPC and ¹H NMR analyses showed that the products obtained were the desired copolymers, with narrow molecular weight distributions (ca. 1.09–1.11) very close to that of the original poly(propylene glycol). ¹H NMR, surface tension measurements, and dynamic light scattering all indicated that the triblock copolymer led to interesting aqueous solution behaviors, including temperature‐induced micellization and very high surface activity. © 2002 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 624–631, 2002; DOI 10.1002/pola.10144     

Synthesis and characterisation of new shell cross-linked micelles with amine-functional coronas

Shell cross-linked (SCL) micelles with amine-functional coronas have been constructed in aqueous solution by exploiting the micellar self-assembly of new thermo-responsive ABC triblock copolymers. These copolymers were prepared via atom transfer radical polymerisation (ATRP) in convenient one-pot syntheses and comprised a thermo-responsive core-forming poly(propylene oxide) [PPO] block, a cross-linkable central poly(glycerol monomethacrylate) [GMA] block and an amine-functional outer block based on either poly(2-(dimethylamino)ethyl methacrylate) [DMA] or poly([2-(methacryloyloxy)ethyl]trimethyl ammonium chloride) [QDMA]. DMF GPC analysis indicated an M_n of 17,700 and an M_w/M_n of 1.46 for the PPO-PGMA-PDMA triblock copolymer. The DMA residues of the PPO-PGMA-PDMA triblock copolymer were reacted with methyl iodide to prepare copolymers with differing degrees of quaternisation. Each triblock copolymer dissolved molecularly in aqueous solution at 5 °C and formed micelles with amine-functional coronas above a critical micelle temperature (CMT) of around 12 °C, which corresponded closely to the cloud point of the PPO macro-initiator. Cross-linking of the GMA residues in the inner shell using divinyl sulfone produced SCL micelles that remained intact at 5 °C, i.e. below the cloud point of the core-forming PPO block. Aqueous electrophoresis studies confirmed that these SCL micelles had considerable cationic surface charge, as expected. The cationic SCL micelles were adsorbed onto a near-monodisperse anionic silica sol, which was used as a model colloidal substrate. Thermogravimetric analyses indicated SCL micelle mass loadings of 6.1-15.5 wt.%, depending on the initial micelle concentration. Aqueous electrophoresis studies confirmed that surface charge reversal occurred on adsorption of the SCL micelles and scanning electron microscopy studies revealed the presence of SCL micelles on the silica particles.     

Amphiphilic ABA triblock copolymer as surfactant in syntheses of microlatexes bearing cationic groups

Polystyrene microlatexes have been prepared by conventional emulsion polymerization with a novel amphiphilic water‐soluble ABA triblock copolymer, poly[2‐(dimethylamino)ethyl methacrylate]₁₅‐b‐poly(propylene oxide)₃₆‐b‐poly[2‐(dimethyl‐amino)ethyl methacrylate]₁₅ (PDMAEMA₁₅‐PPO₃₆‐PDMAEMA₁₅), as a polycationic emulsifier under acidic or neutral conditions. The ABA triblock copolymer was developed by oxyanion‐initiated polymerization in our laboratory. In this study, it acted well both as a polycationic polymeric surfactant to form block copolymeric micelles for emulsion polymerization and as a stabilizer to be anchored into the polystyrene microlatex or adsorbed onto its surface. The results obtained with various copolymer concentrations and different pH media showed that microlatex diameters decreased remarkably with increased concentration of this ABA triblock copolymeric emulsifier, but were not as much affected by the pH of media within the experimental range of 3.4–7.0. The observed difference of the particle sizes from transmission electron microscopy and dynamic light scattering measurements is discussed in terms of the effect of the absorbed surfactants and their electrical double layers. This difference has led to the formation of a cationic polyelectrolyte fringe on the surface of microspheres. The final microlatexes were characterized with respect to total conversion, particle diameter, and particle size distribution as well as colloidal stability. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3734–3742, 2002     

Synthesis and hydrogel formation of fluorine‐containing amphiphilic ABA triblock copolymers

Fluorine‐containing amphiphilic ABA triblock copolymers, poly(2‐hydroxyethyl vinyl ether)‐block‐poly[2‐(2,2,3,3,3‐pentafluoropropoxy)ethyl vinyl ether]‐block‐poly(2‐hydroxyethyl vinyl ether) [poly(HOVE‐b‐PFPOVE‐b‐HOVE)] (HFH), poly[2‐(2,2,3,3,3‐pentafluoropropoxy)ethyl vinyl ether]‐block‐poly(2‐hydroxyethyl vinyl ether)‐block‐poly[2‐(2,2,3,3,3‐pentafluoropropoxy)ethyl vinyl ether] [poly(PFPOVE‐b‐HOVE‐b‐PFPOVE)] (FHF), and poly(n‐butyl vinyl ether)‐block‐poly(2‐hydroxyethyl vinyl ether)‐block‐poly(n‐butyl vinyl ether) [poly(NBVE‐b‐HOVE‐b‐NBVE)] (LHL), were synthesized, and their behavior in water was investigated. The aforementioned polymers were prepared by sequential living cationic polymerization of 2‐acetoxyethyl vinyl ether (AcOVE) and PFPOVE or NBVE, followed by hydrolysis of acetyl groups in polyAcOVE. FHF and LHL formed a hydrogel in water, whereas HFH gave a homogeneous aqueous solution. In addition, the gel‐forming concentration of FHF was much lower than that of corresponding LHL. Surface‐tension measurements of the aqueous polymer solutions revealed that all the triblock copolymers synthesized formed micelles or aggregates above about 1.0 × 10^?4 mol/L. The surface tensions of HFH and FHF solutions above the critical micelle concentration were lower than those of LHL, indicating high surface activity of fluorine‐containing triblock copolymers. Small‐angle X‐ray scattering measurements revealed that HFH formed a core‐shell sperical micelle in 1 wt % aqueous solutions, whereas the other block copolymers caused more conplicated assembly in the solutions. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3751–3760, 2001     

Investigating the effect of randomly methylated β-cyclodextrin/block copolymer molar ratio on the template-directed preparation of mesoporous alumina with tailored porosity

Supramolecular assemblies formed between cyclodextrins and block copolymers can be efficiently used as templates for the preparation of mesoporous materials with controlled porosity. In this work, we use dynamic light scattering (DLS) and viscosity measurements to follow the variations occurring in the size and morphology of the triblock copolymer poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) (P123) micelles in the presence of various amounts of randomly methylated β-cyclodextrin (RAMEB). The results obtained with a series of solution compositions reveal that the cyclodextrin-to-copolymer (RAMEB/P123) molar ratio plays a crucial role in the growth rate of the micelles. At low RAMEB/P123 molar ratios (below ~7.5), a swelling effect of the cyclodextrin in the P123 micelles is noticed together with a modification of the micellar curvature from spherical to ellipsoidal. At high molar ratios (~7.5 and above), an abrupt transition toward large supramolecular assemblies, which no longer resemble micelles, occurs. When the RAMEB-swollen P123 micelles are used as templates to direct the self-assembly of colloidal boehmite nanoparticles, mesoporous γ-Al₂O₃ materials with high surface areas (360–400 m²/g), tunable pore sizes (10–20 nm), large pore volumes (1.3–2.0 cm³/g) and fiberlike morphologies are obtained under mild conditions. The composition of the mixed micellar solution, in particular the cyclodextrin-to-copolymer molar ratio, appears to be a key factor in controlling the porosity of alumina.     

Modulating structural stability and acid sensitivity of photosensitive polymer micelles simply via one‐batch UV irradiation

This article describes the photosensitive polymer micelles whose structural stability and acid sensitivity can be widely tuned simply via one‐batch UV irradiation. To this end, the well‐defined poly(5‐ethyl‐5‐methacryloyloxy‐methyl‐2‐styryl‐[1,3]dioxane)‐block‐poly[poly(ethylene glycol) methacrylate] (PEMSD‐b‐PPEGMA) copolymers were synthesized via RAFT polymerization under mild visible light radiation at 30 °C. The results demonstrated that the irradiation of the homogeneous acetone solution with UV light only induced Z‐isomerization of their cinnamyl groups, while irradiating PEMSD chains in the bulky micellar cores only induced dimerization. Moreover, the micelles of previously Z‐isomerized copolymer could be effectively stabilized without changing their acid sensitivity on irradiating for shortly 3 min, while UV irradiation for 30 min could remarkably improve the acid stability of these micelles. These novel properties are of potential applications in controlled drug delivery. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Synthesis and self-assembly behaviors of well-defined poly(lauryl methacrylate)-block-poly[N-(2-methacryloylxyethyl)pyrrolidone] copolymers

A series of structurally controllable poly(lauryl methacrylate)-b-poly[N-(2-methacryloylxyethyl)pyrrolidone], PLMA-b-PNMP, diblock copolymers were synthesized by reversible addition–fragmentation chain transfer polymerization. The self-assembly behaviors of PLMA-b-PNMP in a selective solvent, tetrahydrofuran (THF), were studied by employing static light scattering, dynamic light scattering, and transmission electron microscopy in detail. The relationships between the aggregation parameters, such as critical micelle concentration and the aggregation number (N _agg), and the molecular structure were established. It was found that spherical micelles can be formed once the solvophobic block length of poly[N-(2-methacryloylxyethyl)pyrrolidone] is larger than 215. Moreover, extremely small and monodisperse gold nanoparticles (<2 nm) were synthesized by employing PLMA-b-PNMP diblock copolymers in THF.     

Well‐defined poly[(dimethylamimo)ethyl methacrylate]‐b‐poly(fluoroalkyl methacrylate) diblock copolymers: Effects of different fluoroalkyl groups on the solution properties

A series of well‐defined, fluorinated diblock copolymers, poly[2‐(dimethylamino)ethyl methacrylate]‐b‐poly(2,2,2‐trifluoroethyl methacrylate) (PDMA‐b‐PTFMA), poly[2‐(dimethylamino)ethyl methacrylate]‐b‐poly(2,2,3,4,4,4‐hexafluorobutyl methacrylate) (PDMA‐b‐PHFMA), and poly[2‐(dimethylamino)ethyl methacrylate]‐b‐poly(2,2,3,3,4,4,5,5‐octafluoropentyl methacrylate) (PDMA‐b‐POFMA), have been synthesized successfully via oxyanion‐initiated polymerization. Potassium benzyl alcoholate (BzO^?K⁺) was used to initiate DMA monomer to yield the first block PDMA. If not quenched, the first living chain could be subsequently used to initiate a feed F‐monomer (such as TFMA, HFMA, or OFMA) to produce diblock copolymers containing different poly(fluoroalkyl methacrylate) moieties. The composition and chemical structure of these fluorinated copolymers were confirmed by ¹H NMR, ¹⁹F NMR spectroscopy, and gel permeation chromatography (GPC) techniques. The solution behaviors of these copolymers containing (tri‐, hexa‐, or octa‐ F‐atom)FMA were investigated by the measurements of surface tension, dynamic light scattering (DLS), and UV spectrophotometer. The results indicate that these fluorinated copolymers possess relatively high surface activity, especially at neutral media. Moreover, the DLS and UV measurements showed that these fluorinated diblock copolymers possess distinct pH/temperature‐responsive properties, depending not only on the PDMA segment but also on the fluoroalkyl structure of the FMA units. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2702–2712, 2009     

Stimuli‐responsive ABC triblock copolymers by sequential living cationic copolymerization: Multistage self‐assemblies through micellization to open association

Stimuli‐responsive ABC triblock copolymers with three segments with different phase‐separation temperatures were synthesized via sequential living cationic copolymerization. The triblock copolymers exhibited sensitive thermally induced physical gelation (open association) through the formation of micelles. For example, an aqueous solution of EOVE₂₀₀‐b‐MOVE₂₀₀‐b‐EOEOVE₂₀₀ [where EOVE is 2‐ethoxyethyl vinyl ether, MOVE is 2‐methoxethyl vinyl ether and EOEOVE is 2‐(2‐ethoxy)ethoxyethyl vinyl ether; the order of the phase‐separation temperatures was poly(EOVE) (20 °C) < poly(EOEOVE) (41 °C) < poly(MOVE) (70 °C)] underwent multiple reversible transitions from sol (<20 °C) to micellization (20–41 °C) to physical gelation (physical crosslinking, 41–64 °C) and, finally, to precipitation (>64 °C). At 41–64 °C, the physical gel became stiffer than similar diblock or ABA triblock copolymers of the same molecular weight. Furthermore, the ABC triblock copolymers exhibited Weissenberg effects in semidilute aqueous solutions. In sharp contrast, another ABC triblock copolymer with a different arrangement, EOVE₂₀₀‐b‐EOEOVE₂₀₀‐b‐MOVE₂₀₀, scarcely exhibited any increase in viscosity above 41 °C. The temperatures of micelle formation and physical gelation corresponded to the phase‐separation temperatures of the segment types in the ABC triblock copolymer. No second‐stage association was observed for AB and ABA block copolymers with the same thermosensitive segments found in their ABC counterparts. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2601–2611, 2004     

Behaviors of self‐assembled diblock copolymer with pendant photosensitive azobenzene segments

A novel monomer, ethyl 4‐[4‐(11‐methacryloyloxyundecyloxy)phenyl azobenzoyl‐oxyl] benzoate, containing a photoisomerizable N?N group was synthesized. The monomer was further diblock copolymerized with methyl methacrylate. Amphiphilic diblock copolymer poly(methyl methacrylate‐block‐ethyl 4‐[4‐(11‐methacryloyloxyundecyloxy)phenyl azobenzoyl‐oxyl] benzoate ( PMMA ‐ b ‐ PAzoMA ) was synthesized using atom transfer radical polymerization. The reverse micelles with spherical construction were obtained with 2 wt % of the diblock copolymer in a THF/H₂O mixture of 1:2. Under alternating UV and visible light illumination, reversible changes in micellar structure between sphere and rod‐like particles took place as a result of the reversible E‐Z photoisomerization of azobenzene segments in PMMA ‐ b ‐ PAzoMA . Microphase separation of the amphiphilic diblock copolymer in thin films was achieved through thermal and solvent aligning methods. The microphases of the annealed thin films were investigated using atom force microscopy topology and scanning electron microscopy analyses. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1142–1148, 2010     

Enhanced DOX loading in star-like benzyl functionalized polycaprolactone micelles

The self-assembly of functionalized polycaprolactone amphiphilic diblock copolymers is explored for carrier-mediated doxorubicin delivery for cancer treatment. In this report, functionalized polycaprolactone-based amphiphilic block copolymers with controlled branching architecture are investigated. Star-like copolymers, namely 4-arm and 6-arm poly(γ-benzyloxy-ε-caprolactone)-b-poly{γ-2-[2-(2-methoxyethoxy)ethoxy]ethoxy-ε-caprolactone} (PBCL-b-PMEEECL) were synthesized by living ring-opening block copolymerization (ROP) of γ-(2-benzyloxy)-ε-caprolactone and γ-2-[2-(2-methoxyethoxy)ethoxy]ethoxy-ε-caprolactone using multifunctional initiators. A systematic investigation of the effect of branching points on polymer properties and micellar carrier properties was carried out. The star-like PBCL-b-PMEEECL micelles displayed better thermodynamic stability, size reduction, and enhanced doxorubicin encapsulation than the linear PBCL-b-PMEEECL. Furthermore, the π–π stacking between the benzyl group of the hydrophobic PBCL core and the doxorubicin, the anti-cancer drug, also increases the stability and loading capacity of the micelles. The star-polymers display tunable thermoresponsivity in the range of 40–42°C. When the DOX-loaded micelles are accumulated in the tumor, the shell of the polymeric micelles dehydrates upon heating (at a temperature above its LCST), causing disassembling of the micelles and releasing of DOX. Compared with DOX-loaded linear and 4-arm micelles, DOX-loaded 6-arm micelles exhibited higher in vitro anti-tumor activity. Thus, the 6-arm benzyl substituted polycaprolactone-based micellar systems are promising candidates for drug delivery applications.     

Syntheses of amphiphilic biodegradable copolymers of poly(ethyl ethylene phosphate) and poly(3-hydroxybutyrate) for drug delivery

Biodegradable and amphiphilic triblock copolymers poly(ethyl ethylene phosphate)-poly(3-hydroxy-butyrate)-poly(ethyl ethylene phosphate) (PEEP-b-PHB-b-PEEP) have been successfully synthesized through ring-opening polymerization. The structures are confirmed by gel permeation chromatography and NMR analyses. Crystallization investigated by X-ray diffraction reveals that the block copolymer with higher content of poly(ethyl ethylene phosphate) (PEEP) is more amorphous, showing decreased crystallizability. The obtained copolymers self-assemble into biodegradable nanoparticles with a core-shell micellar structure in aqueous solution, verified by the probe-based fluorescence measurements and transmission electronic microscopy (TEM) observation. The hydrophobic poly(3-hydroxybutyrate) (PHB) block serves as the core of the micelles and the micelles are stabilized by the hydrophilic PEEP block. The size and size distribution are related to the compositions of the copolymers. Paclitaxel (PTX) has been encapsulated into the micelles as a model drug and a sustained drug release from the micelles is observed. MTT assay also demonstrates that the block copolymers are biocompatible, rendering these copolymers attractive for drug delivery. Supported by the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No.20060358036)     

Amphiphilic block glycopolymers via atom transfer radical polymerization: Synthesis,self‐assembly and biomolecular recognition

In this work the synthesis of poly(butyl acrylate)‐b‐poly(2‐{[(D ‐glucosamin‐2‐N‐yl)carbonyl]oxy}ethyl methacrylate) (PBA‐b‐PHEMAGl) diblock glycopolymer and poly(2‐{[(D ‐glucosamin‐2‐N‐yl)carbonyl]oxy}ethyl methacrylate)‐b‐poly(butyl acrylate)‐b‐poly(2‐{[(D ‐glucosamin‐2‐N‐yl)carbonyl]oxy}ethyl methacrylate) (PHEMAGl‐b‐PBA‐b‐PHEMAGl) was performed via atom transfer radical polymerization. Monofunctional and difunctional poly(butyl acrylate) macroinitiators were used to synthesize the well‐defined diblock and triblock glycopolymers by chain extension reaction with the glycomonomer HEMAGl. The self‐assembly of these glycopolymers in aqueous solution was studied by dynamic light scattering and transmission electron microcopy, showing the coexistence of spherical micelles and polymeric vesicles. In addition, the biomolecular recognition capacity of these micelles and vesicles, containing glucose moieties in their coronas, was investigated using the lectin Concanavalin A, Canavalia Ensiformis, which specifically interacts with glucose groups. The binding capacity of Concanavalin A with glycopolymer is influenced by the copolymer composition, increasing with the length of HEMAGl glycopolymer segment in the block copolymer. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Physicochemical characterization of the thermo‐induced self‐assembly of thermo‐responsive PDMAEMA‐b‐PDEGMA copolymers

Diblock copolymers of poly[2‐(dimethylamino)ethyl methacrylate]‐block‐poly[di(ethylene glycol) methyl ether methacrylate], PDMAEMA‐b‐PDEGMA, were synthesized by reversible addition–fragmentation chain transfer polymerization. The block ratio was varied to study the influence on the lower critical solution temperature and the corresponding phase transition in water. Therefore, turbidimetry, differential scanning calorimetry (DSC), dynamic light scattering (DLS), and laser Doppler velocimetry were applied. Additionally, asymmetric flow field‐flow fractionation (AF4) coupled to DLS and multiangle laser light scattering (MALLS) was established as an alternative route to characterize these systems in terms of molar mass of the polymer chain and size of the colloids after the phase transition. It was found that AF4–MALLS allowed accurate determination of molar masses in the studied range. Nevertheless, some limitations were observed, which were critically discussed. The cloud point and phase transition of all materials, as revealed by turbidimetry, could be confirmed by DSC. For block copolymers with block ratios in the range of 50:50, a thermo‐induced self‐assembly into micellar and vesicular structures with hydrodynamic radii (R_h) of around 25 nm was observed upon heating. At higher temperatures, a reordering of the self‐assembled structures could be detected. The thermo‐responsive behavior was further investigated in dependence of pH value and ionic strength. Variation of the pH value mainly influences the solubility of the PDMAEMA segment, where a decrease of the pH value increases the transition temperature. An increase of ionic strength leads to a reduction of the cloud point due to the screening of electrostatic interactions. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 924–935     

Thermoresponsive star triblock copolymers by combination of ROP and ATRP: From micelles to hydrogels

Novel biocompatible, biodegradable, four‐arm star, triblock copolymers containing a hydrophobic poly(ε‐caprolactone) (PCL) segment, a hydrophilic poly(oligo(ethylene oxide)475 methacrylate) (POEOMA475) segment and a thermoresponsive poly(di(ethylene oxide) methyl ether methacrylate) (PMEO₂MA) segment were synthesized by a combination of controlled ring‐opening polymerization (ROP) and atom transfer radical polymerization (ATRP). First, a four‐arm PCL macroinitiator [(PCL‐Br)₄] for ATRP was synthesized by the ROP of ε‐caprolactone (CL) catalyzed by stannous octoate in the presence of pentaerythritol as the tetrafunctional initiator followed by esterification with 2‐bromoisobutyryl bromide. Then, sequential ATRP of oligo(ethylene oxide) methacrylate (OEOMA475, M_n = 475) and di(ethylene oxide) methyl ether methacrylate) (MEO₂MA) were carried out using the (PCL‐Br)₄ tetrafunctional macroinitiator, in different sequence, resulting in preparation of (PCL‐b‐POEOMA475‐b‐PMEO₂MA)₄ and (PCL‐b‐PMEO₂MA‐b‐POEOMA475)₄ star triblock copolymers. These amphiphilic copolymers can self‐assemble into spherical micelles in aqueous solution at room temperature. The thermal responses of the polymeric micelles were investigated by dynamic light scattering and ultraviolet spectrometer. The properties of the two series of copolymers are quite different and depend on the sequence distribution of each block along the arms of the star. The (PCL‐b‐POEOMA475‐b‐PMEO₂MA)₄ star copolymer, with the thermoresponsive PMEO₂MA segment on the periphery, can undergo reversible sol‐gel transitions between room temperature (22 °C) and human body temperature (37 °C). © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Hierarchically organized micellization of thermoresponsive rod‐coil copolymers based on poly[oligo(ethylene glycol) methacrylate] and poly(ε‐caprolactone)

A series of amphiphilic triblock copolymers, poly[oligo(ethylene glycol) methacrylate]_x‐block‐poly(ε‐caprolactone)‐block‐poly[oligo(ethylene glycol) methacrylate]_x, POEGMA_Co(x), were synthesized. Formation of hydrophobic domains as cores of the micelles was studied by fluorescence spectroscopy. The critical micelle concentrations in aqueous solution were found to be in the range of circa 10^?6 M. A novel methodology by modulated temperature differential scanning calorimetry was developed to determine critical micelle temperature. A significant concentration dependence of cmt was found. Dynamic light scattering measurements showed a bidispersed size distribution. The micelles showed reversible dispersion/aggregation in response to temperature cycles with lower critical solution temperature between 75 and 85 °C. The interplay of the two hydrophobic and one thermoresponsive macromolecular chains offers the chance to more complex morphologies. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Synthesis and micelle formation of triblock copolymers of poly(methyl methacrylate)-b-poly(ethylene oxide)-b-poly(methyl methacrylate) in aqueous solution

Amphiphilic triblock copolymers of poly(methyl methacrylate)-b-poly(ethylene oxide)-b-poly(methyl methacrylate) (PMMA-b-PEO-b-PMMA) with well-defined structure were synthesized via atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) initiated by the PEO macroinitiator. The macroinitiator and triblock copolymer with different PMMA and/or PEO block lengths were characterized with ¹H and ¹³C NMR and gel permeation chromatography (GPC). The micelle formed by these triblock copolymers in aqueous solutions was detected by fluorescence excitation and emission spectra of pyrene probe. The critical micelle concentration (CMC) ranged from 0.0019 to 0.016 mg/mL and increased with increasing PMMA block length, while the PEO block length had less effect on the CMC. The partition constant K_v for pyrene in the micelle and in aqueous solution was about 10⁵. The triblock copolymer appeared to form the micelles with hydrophobic PMMA core and hydrophilic PEO loop chain corona. The hydrodynamic radius R_h,app of the micelle measured with dynamic light scattering (DLS) ranged from 17.3 to 24.0 nm and increased with increasing PEO block length to form thicker corona. The spherical shape of the micelle of the triblock copolymers was observed with an atomic force microscope (AFM). Increasing hydrophobic PMMA block length effectively promoted the micelle formation in aqueous solutions, but the micelles were stable even only with short PMMA blocks.