Heteroarm Star‐Like Micelles Formed from Polystyrene‐block‐poly(2‐vinyl pyridine)‐block‐poly(methyl methacrylate) ABC Triblock Copolymers in Toluene

Polystyrene‐block‐poly(2‐vinyl pyridine)‐block‐poly(methyl methacrylate) ABC triblock copolymers were synthesized by sequential living anionic polymerization. Their solution properties were investigated in toluene, which is a bad solvent for the middle block. Spherical micelles are formed, which consist of a poly(2‐vinyl pyridine) dense core bearing polystyrene and poly(methyl methacrylate) soluble chains at the corona. These micelles exhibit the architecture of heteroarm star copolymers obtained by “living” polymerization methods. The aggregation numbers strongly depend on the length of the insoluble P2VP middle block, thus remarkably affecting the size of the micelles.     

Poly(N‐vinyl pyrrolidone)‐block‐Poly(N‐vinyl carbazole)‐block‐poly(N‐vinyl pyrrolidone) triblock copolymers: Synthesis via RAFT/MADIX process,self‐assembly behavior,and photophysical properties

Poly(N‐vinyl pyrrolidone)‐block‐poly(N‐vinyl carbazole)‐block‐poly(N‐vinyl pyrrolidone) (PVP‐b‐PVK‐b‐PVP) triblock copolymers were synthesized via sequential reversible addition‐fragmentation chain transfer/macromolecular design via the interchange of xanthate (RAFT/MADIX) process. First, 1,4‐phenylenebis(methylene)bis(ethyl xanthate) was used as a chain transfer agent to mediate the radical polymerization of N‐vinyl carbazole (NVK). It was found that the polymerization was in a controlled and living manner. Second, one of α,ω‐dixanthate‐terminated PVKs was used as the macromolecular chain transfer agent to mediate the radical polymerization of N‐vinyl pyrrolidone (NVP) to obtain the triblock copolymers with various lengths of PVP blocks. Transmission electron microscopy (TEM) showed that the triblock copolymers in bulks were microphase‐separated and that PVK blocks were self‐organized into cylindrical microdomains, depending on the lengths of PVP blocks. In aqueous solutions, all these triblock copolymers can self‐assemble into the spherical micelles. The critical micelle concentrations of the triblock copolymers were determined without external adding fluorescence probe. By analyzing the change in fluorescence intensity as functions of the concentration, it was judged that the onset of micellization occurred at the concentration while the FL intensity began negatively to deviate from the initial linear increase with the concentration. Fluorescence spectroscopy indicates that the self‐assembled nanoobjects of the PVP‐b‐PVK‐b‐PVP triblock copolymers in water were capable of emitting blue/or purple fluorescence under the irradiation of ultraviolet light. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1852–1863     

Photocrosslinked poly(vinylbenzophenone)‐core micelles via mild Friedel–Crafts benzoylation of polystyrene amphiphiles

Photocrosslinkable poly(vinylbenzophenone)‐containing polymers were synthesized via a one‐step, Friedel–Crafts benzoylation of polystyrene‐containing starting materials [including polystyrene, polystyrene‐block‐poly(tert‐butyl acrylate), polystyrene‐block‐poly(ethylene oxide), polystyrene‐block‐poly(methyl methacrylate), and polystyrene‐block‐poly(n‐butyl acrylate)] with benzoyl trifluoromethanesulfonate as a benzoylation reagent. The use of this mild reagent (which required no added Lewis acid) permitted polymers with well‐defined compositions and narrow molecular weight distributions to be synthesized. Micelles formed from one of these benzoylated polymers, [polystyrene_0.25‐co‐poly(vinylbenzophenone)_0.75]₁₁₅‐block‐poly(acrylic acid)₁₄, were then fixed by the irradiation of the micelle cores with UV light. As the irradiation time was increased, the pendent benzophenone groups crosslinked with other chains in the glassy micelle cores. Dynamic light scattering, spectrofluorimetry, and Fourier transform infrared spectroscopy were all used to verify the progress of the crosslinking reaction. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2604–2614, 2006     

Synthesis and characterization of side‐chain liquid crystalline ABC triblock copolymers with p‐methoxyazobenzene moieties by atom transfer radical polymerization

A series of novel side‐chain liquid crystalline ABC triblock copolymers composed of poly(ethylene oxide) (PEO), polystyrene (PS), and poly[6‐(4‐methoxy‐4′‐oxy‐azobenzene) hexyl methacrylate] (PMMAZO) were synthesized by atom transfer radical polymerization (ATRP) using CuBr/1,1,4,7,7‐pentamethyldiethylenetriamine (PMDETA) as a catalyst system. First, the bromine‐terminated diblock copolymer poly(ethylene oxide)‐block‐polystyrene (PEO‐PS‐Br) was prepared by the ATRP of styrene initiated with the macro‐initiator PEO‐Br, which was obtained from the esterification of PEO and 2‐bromo‐2‐methylpropionyl bromide. An azobenzene‐containing block of PMMAZO with different molecular weights was then introduced into the diblock copolymer by a second ATRP to synthesize the novel side‐chain liquid crystalline ABC triblock copolymer poly(ethylene oxide)‐block‐polystyrene‐block‐poly[6‐(4‐methoxy‐4′‐oxy‐azobenzene) hexyl methacrylate] (PEO‐PS‐PMMAZO). These block copolymers were characterized using proton nuclear magnetic resonance (¹H NMR) and gel permeation chromatograph (GPC). Their thermotropic phase behaviors were investigated using differential scanning calorimetry (DSC) and polarized optical microscope (POM). These triblock copolymers exhibited a smectic phase and a nematic phase over a relatively wide temperature range. At the same time, the photoresponsive properties of these triblock copolymers in chloroform solution were preliminarily studied. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4442–4450, 2008     

Bis‐hydrophilic and functional triblock terpolymers based on polyethers: Synthesis and self‐assembly in solution

A well‐defined triblock terpolymer, poly(ethylene glycol)‐block‐poly(allyl glycidyl ether)‐block‐poly(tert‐butyl glycidyl ether) (PEG‐b‐PAGE‐b‐Pt‐BGE), with a narrow molar mass distribution has been synthesized by sequential living anionic ring‐opening polymerization. Afterward, the PAGE block was modified via thiol‐ene chemistry and different sugar moieties or cysteine as a model compound for peptides could be covalently attached to the polymer backbone. The solution self‐assembly of the obtained bis‐hydrophilic triblock terpolymers in aqueous media has been studied in detail by turbidimetry, dynamic light scattering, and transmission electron microscopy (TEM and cryo‐TEM). © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Synthesis of poly(tert‐butyl acrylate‐block‐vinyl acetate) copolymers by combining ATRP and RAFT polymerizations

The synthesis of poly(tert‐butyl acrylate‐block‐vinyl acetate) copolymers using a combination of two living radical polymerization techniques, atom transfer radical polymerization (ATRP) and reversible addition‐fragmentation chain transfer (RAFT) polymerization, is reported. The use of two methods is due to the disparity in reactivity of the two monomers, viz. vinyl acetate is difficult to polymerize via ATRP, and a suitable RAFT agent that can control the polymerization of vinyl acetate is typically unable to control the polymerization of tert‐butyl acrylate. Thus, ATRP was performed to make poly(tert‐butyl acrylate) containing a bromine end group. This end group was subsequently substituted with a xanthate moiety. Various spectroscopic methods were used to confirm the substitution. The poly(tert‐butyl acrylate) macro‐RAFT agent was then used to produce (tert‐butyl acrylate‐block‐vinyl acetate). © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7200–7206, 2008     

Synthesis of amphiphilic ABC triblock copolymers by single electron transfer nitroxide radical coupling reaction in tetrahydrofuran

A series of ABC triblock copolymers, that is, polyisoprene‐block‐polystyrene‐block‐poly(ethylene oxide) (PI‐PS‐PEO), PI‐block‐poly(tert‐butyl acrylate)‐block‐PEO (PI‐PtBA‐PEO), and PI‐block‐poly(acrylic acide)‐block‐PEO (PI‐PAA‐PEO) were obtained by combination of anionic technique, atom transfer radical polymerization (ATRP), and single electron transfer nitroxide coupling (SETNRC) reaction. Anionic polymerization of isoprene followed by end capping with ethylene oxide yielded hydroxyl‐terminated PI. After esterification, PI with Br end group was used as a macroinitiator to initiate the polymerization of styrene and tBA by ATRP that was then trapped by 2,2,6,6‐tetramethylpiperidine‐1‐oxyl (TEMPO) group in PEO by SETNRC reaction rapidly with high efficiency in tetrahydrofuran at room temperature. The effect of reaction time and polymer chain length on SETNRC reaction was discussed in detail. In the presence of Cu⁰/tris[2‐(dimethylamino)ethyl]amine, SETNRC between PI‐PS‐Br and PEO‐TEMPO was carried out with the efficiency of up to 91.6% in 2 h. With the increase in polymer chain length, the efficiency decreased fleetly. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Radiation‐induced fabrication of polymer nanoporous materials from microphase‐separated structure of diblock copolymers as a template

Polymer nanoporous materials with periodic cylindrical holes were fabricated from microphase‐separated structure of diblock copolymers consisting of a radiation‐crosslinking polymer and a radiation‐degrading polymer through simultaneous crosslinking and degradation by γ‐irradiation. A polybutadiene‐block‐poly(methyl methacrylate) (PB‐b‐PMMA) diblock copolymer film that self‐assembles into hexagonally packed poly(methyl methacrylate) cylinders in polybutadiene matrix was irradiated with γ‐rays. Solubility test, IR spectroscopy, and TEM and SEM observations for this copolymer film in comparison with a polystyrene‐block‐poly(methyl methacrylate) diblock copolymer film revealed that poly(methyl methacrylate) domains were removed by γ‐irradiation and succeeding solvent washing to form cylindrical holes within polybutadiene matrix, which was rigidified by radiation crosslinking. Thus, it was demonstrated that nanoporous materials can be prepared by γ‐irradiation, maintaining the original structure of PB‐b‐PMMA diblock copolymer film. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5916–5922, 2007     

Linear pentablock quintopolymers (l‐SIDMV) with five incompatible blocks: Polystyrene,polyisoprene‐1,4, poly(dimethylsiloxane), poly(tert‐butyl methacrylate), and poly(2‐vinylpyridine)

Three linear pentablock quintopolymers (l‐SIDMV), where S is polystyrene (PS), I polyisoprene‐1,4 (PI), D poly(dimethylsiloxane) (PDMS), M poly(tert‐butyl methacrylate) (PtBuM), and V poly(2‐vinylpyridine) (P2VP), were synthesized by anionic polymerization high vacuum techniques. The approach involves the following: (a) The synthesis of living triblock terpolymer PS‐b‐PI‐b‐PDMSLi and diblock copolymer P2VP‐b‐PtBuMK by sequential polymerizations of the corresponding monomers with sec‐BuLi and benzyl potassium, respectively; and (b) The selective linking of the living triblock terpolymer with the chlorosilane group of 2‐(chloromethylphenyl)ethyldimethylchlorosilane (CMPDMS), followed by linking of the living block copolymer with the remaining chloromethyl group of CMPDMS. Molecular characterization carried out by size exclusion chromatography, membrane osmometry, solution (in CDCl₃ or d₈‐toluene) and solid‐state ¹H‐NMR spectroscopy indicated a high degree of molecular and compositional homogeneity. Differential scanning calorimetry results on the precursors and final polymers were discussed. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3938–3946, 2008     

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     

pH/Thermosensitive Hydrogels Formed at Low pH by a PMMA‐PAA‐P2VP‐PAA‐PMMA Pentablock Terpolymer

A poly(methyl methacrylate)‐block‐poly(acrylic acid)‐block‐poly(2‐vinyl pyridine)‐block‐poly(acrylic acid)‐block‐poly(methyl methacrylate) (PMMA‐PAA‐P2VP‐PAA‐PMMA), pentablock terpolymer has been synthesized by anionic polymerization with sequential addition of monomers and studied in aqueous media at low pH. The system exhibits combined properties and adopts the behavior of ‘telechelic’ polyelectrolytes and that of double hydrophilic polyampholytes. This complex behavior leads to the pentablock terpolymer forming a pH and temperature sensitive reversible hydrogel at very low polymer concentration.

     

Amphiphilic star‐block copolymers based on a hyperbranched core: Synthesis and supramolecular self‐assembly

Novel amphiphilic star‐block copolymers, star poly(caprolactone)‐block‐poly[(2‐dimethylamino)ethyl methacrylate] and poly(caprolactone)‐block‐poly(methacrylic acid), with hyperbranched poly(2‐hydroxyethyl methacrylate) (PHEMA–OH) as a core moiety were synthesized and characterized. The star‐block copolymers were prepared by a combination of ring‐opening polymerization and atom transfer radical polymerization (ATRP). First, hyperbranched PHEMA–OH with 18 hydroxyl end groups on average was used as an initiator for the ring‐opening polymerization of ε‐caprolactone to produce PHEMA–PCL star homopolymers [PHEMA = poly(2‐hydroxyethyl methacrylate); PCL = poly(caprolactone)]. Next, the hydroxyl end groups of PHEMA–PCL were converted to 2‐bromoesters, and this gave rise to macroinitiator PHEMA–PCL–Br for ATRP. Then, 2‐dimethylaminoethyl methacrylate or tert‐butyl methacrylate was polymerized from the macroinitiators, and this afforded the star‐block copolymers PHEMA–PCL–PDMA [PDMA = poly(2‐dimethylaminoethyl methacrylate)] and PHEMA–PCL–PtBMA [PtBMA = poly(tert‐butyl methacrylate)]. Characterization by gel permeation chromatography and nuclear magnetic resonance confirmed the expected molecular structure. The hydrolysis of tert‐butyl ester groups of the poly(tert‐butyl methacrylate) blocks gave the star‐block copolymer PHEMA–PCL–PMAA [PMAA = poly(methacrylic acid)]. These amphiphilic star‐block copolymers could self‐assemble into spherical micelles, as characterized by dynamic light scattering and transmission electron microscopy. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 6534–6544, 2005     

Synthesis,surface properties,and morphologies of poly[methyl(3,3,3‐trifluoropropyl)siloxane]‐b‐polystyrene‐b‐poly(tert‐butyl acrylate) triblock copolymers by a combination of anionic ROP and ATRP

A series of well‐defined poly[methyl(3,3,3‐trifluoropropyl)siloxane]‐b‐polystyrene‐b‐poly(tert‐butyl acrylate) (PMTFPS‐b‐PS‐b‐PtBA) triblock copolymers were prepared by a combination of anionic ring‐opening polymerization of 1,3,5‐trimethyl‐1,3,5‐tris(3′,3′,3′‐trifluoropropyl)cyclotrisiloxane (F₃), and atom transfer radical polymerization (ATRP) of styrene (St) and tert‐butyl acrylate (tBA), using the obtained α‐bromoisobutyryl‐terminal PMTFPS (PMTFPS‐Br) as the macroinitiators. The ATRP of St from PMTFPS‐Br, as well as the ATRP of tBA from the obtained PMTFPS‐b‐PS‐Br macroinitiators, has typical characteristic of controlled/living polymerization. The results of contact angle measurements for the films of PMTFPS‐b‐PS‐b‐PtBA triblock copolymers demonstrate that the compositions have an effect on the wetting behavior of the copolymer films. For the copolymer films with different compositions, there may be different macroscale or nanoscale structures on the outmost layer of the copolymer surfaces. The films with high content of PtBA blocks exhibit almost no ordered microstructures on the outmost layer of the copolymer surfaces, even though they have microphase‐separated structures in bulk. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Microphase‐separated structure of 1,3‐cyclohexadiene/butadiene triblock copolymers and its effect on mechanical and thermal properties

We report the effect of microphase‐separated structure on the mechanical and thermal properties of several poly(1,3‐cyclohexadiene‐block‐butadiene‐block‐1,3‐cyclohexadiene) triblock copolymers (PCHD‐block‐PBd‐block‐PCHD) and of their hydrogenated derivatives: poly(cyclohexene‐block‐ethylene/butylene‐block‐cyclohexene) triblock copolymers (PCHE‐block‐PEB‐block‐PCHE). Both mechanical strength and heat‐resistant temperature (ex. Vicat Softening Temperature: VSPT) tended to increase with an increase in the 1,3‐cyclohexadiene (CHD)/butadiene ratio. On the other hand, heat resistance of the hydrogenated block copolymer was found to be higher than that of the unhydrogenated block copolymer. However, the mechanical strength was lower than those of the unhydrogenated block copolymer with the same ratio of CHD to butadiene. To clarify the relationship between the higher order structures of those block copolymers and their properties, we observed the microphase‐separated structure by transmission electron microscope (TEM). Hydrogenated block copolymers were found to have more finely dispersed microphase‐separated structures than those of the unhydrogenated block copolymers with the same CHD/Bd ratios through the use of TEM and the small‐angle X‐ray scattering (SAXS) technique. Those results indicated that the segregation strength between the PCHE block sequence and the PEB block sequence increased, depending on hydrogenation of the unhydrogenated precursor. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 13–22, 2001     

Synthesis and characterization of novel resorcinarene‐centered amphiphilic star‐block copolymers consisting of eight ABA triblock arms by combination of ROP,ATRP, and click chemistry

Novel amphiphilic eight‐arm star triblock copolymers, star poly(ε‐caprolactone)‐block‐poly(acrylic acid)‐block‐poly(ε‐caprolactone)s (SPCL‐PAA‐PCL) with resorcinarene as core moiety were prepared by combination of ROP, ATRP, and “click” reaction strategy. First, the hydroxyl end groups of the predefined eight‐arm SPCLs synthesized by ROP were converted to 2‐bromoesters which permitted ATRP of tert‐butyl acrylate (tBA) to form star diblock copolymers: SPCL‐PtBA. Next, the bromide end groups of SPCL‐PtBA were quantitatively converted to terminal azides by NaN₃, which were combined with presynthesized alkyne‐terminated poly(ε‐caprolactone) (A‐PCL) in the presence of Cu(I)/N,N,N′,N″,N″‐pentamethyldiethylenetriamine in DMF to give the star triblock copolymers: SPCL‐PtBA‐PCL. ¹H NMR, FTIR, and SEC analyses confirmed the expected star triblock architecture. The hydrolysis of tert‐butyl ester groups of the poly(tert‐butyl acrylate) blocks gave the amphiphilic star triblock copolymers: SPCL‐PAA‐PCL. These amphiphilic star triblock copolymers could self‐assemble into spherical micelles in aqueous solution with the particle size ranging from 20 to 60 nm. Their micellization behaviors were characterized by dynamic light scattering and transmission electron microscopy. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2905–2916, 2009     

Synthesis and characterization of a biodegradable ABC triblock terpolymer as co‐delivery carrier of doxorubicin and DNA

This study is aimed to develop a well‐defined ABC triblock terpolymer, poly(ethylethylene phosphate)‐block‐poly(ε‐caprolactone)‐block‐poly[2‐(dimethylamino)ethyl methacrylate] (PEEP‐b‐PCL‐b‐PDMAEMA), for co‐encapsulating anticancer drug doxorubicin (DOX) and DNA to form polyplexes. The terpolymer is first synthesized via a combination of ring‐opening polymerization and atom‐transfer radical polymerization techniques, and characterized by ¹H NMR and gel permeation chromatography. Subsequently, the self‐assembly behavior of the terpolymer and the micelles loaded with DOX or DNA are investigated by dynamic light scattering, ζ potential, transmission electron microscopy, and gel retardation assay, respectively. In vitro release study reveals that much more DOX is released at pH 5.0 than that at pH 7.4 in the same period. The simultaneous delivery of DOX and green fluorescent protein (GFP)‐labeled DNA is studied by a fluorescence microscope and the results demonstrate that both drug and GFP–DNA can be efficiently delivered into HeLa cells. This system presents a practical and promising carrier for the co‐delivery of drugs and genes. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 3005–3016     

Modular synthesis of ABC type block copolymers by “click” chemistry

Heterotelechelic polystyrene (PS), poly(tert‐butyl acrylate) (PtBA), and poly (methyl acrylate) (PMA), containing both azide and triisopropylsilyl (TIPS) protected acetylene end groups, were prepared in good control (M_w/M_n ≤ 1.24) by atom transfer radical polymerization (ATRP). The end groups were independently applied in two successive “click” reactions, that is: first the azide termini were functionalized and, after deprotection, the acetylene moieties were utilized for a second conjugation step. As a proof of concept, PS was consecutively functionalized with propargyl alcohol and azidoacetic acid, as confirmed by MALDI‐ToF MS. In addition, the same methodology was employed to modularly build up an ABC type triblock terpolymer. Size exclusion chromatography measurements demonstrated first coupling of PtBA to PS and, after the deprotection of the acetylene functionality on PS, connection of PMA, yielding a PMA‐b‐PS‐b‐PtBA triblock terpolymer. The reactions were driven to completion using a slight excess of azide functionalized polymers. Reduction of the residual azide groups into amines allowed easy removal of this excess of polymer by column chromatography. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2913–2924, 2007     

Self‐assembly of a triblock terpolymer mediated by hydrogen‐bonded complexes

A poly(methyl methacrylate)‐block‐poly(4‐vinylpyridine)‐block‐polystyrene (PMMA‐b‐P4VP‐b‐PS) triblock terpolymer is synthesized by ATRP to study its self‐assembly with PAA in organic solvents. The self‐assembly behavior of this system is compared with the one of a mixture of two diblocks, namely polystyrene‐block‐poly(4‐vinylpyridine) (PS‐b‐P4VP) and poly(methyl methacrylate)‐block‐poly(methacrylic acid) (PMMA‐b‐PMAA). For both systems, formation of hydrogen‐bonded complexes between the P4VP and PMAA or PAA blocks occurs. These complexes become insoluble in the solvent used and micelles with a P4VP/P(M)AA complexes core surrounded by PS and PMMA coronal chains are obtained in both cases. These micelles are analyzed by DLS and TEM. Spherical micelles are formed for both systems but the hydrodynamic radii obtained for the two types of micelles are different. Indeed, the micelles formed by the PMMA‐b‐P4VP‐b‐PS + PAA system are smaller than those observed for the PS‐b‐P4VP + PMMA‐b‐PMAA system. Finally, the effect of the molar ratio of the P4VP/PMAA complexing blocks is investigated. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 459–467     

Synthesis and characterization of biodegradable triblock copolymers based on bacterial poly[(R)‐3‐hydroxybutyrate] by atom transfer radical polymerization

Biodegradable poly(tert‐butyl acrylate)–poly[(R)‐3‐hydroxybutyrate]–poly (tert‐butyl acrylate) triblock copolymers based on bacterial poly[(R)‐3‐hydroxybutyrate] (PHB) were synthesized by atom transfer radical polymerization. The chain architectures of the triblock copolymers were confirmed by ¹H NMR and ¹³C NMR spectra. Gel permeation chromatography analysis was used to estimate the molecular weight characteristics and lengths of the PHB and poly(tert‐butyl acrylate) blocks of the copolymers. The thermal properties of the copolymers were studied by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). TGA showed that the triblock copolymers underwent stepwise thermal degradation and had better thermal stability than their respective homopolymers, whereas DSC analyses showed that a microphase‐separation structure was formed only in the triblock copolymers with the longer PHB block. As a similar result, from wide‐angle X‐ray diffraction experimentation, the crystalline phase of PHB could not be seen evidently in the triblock copolymers with the shorter PHB block. The enzymatic hydrolysis of the copolymer films was carried at 37 °C and pH 7.4 in a potassium phosphate buffer with an extracellular PHB depolymerase from Penicillum sp. The biodegradability of the triblock copolymers increased with an increase in the PHB block content. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4857–4869, 2005     

A new way to the “knitting pattern” via blending of ABC triblock copolymers

The “knitting pattern” morphology was obtained via blending of two polystyrene-block-polybutadiene-block-poly(methyl methacrylate) triblock copolymers. This demonstrates that blending of block copolymers is a useful way to design periodic superstructures by taking advantage of the self-assembling nature of microphase separated block copolymers.