Poly(p‐phenylene methylene)‐based block copolymers by mechanistic transformation

The synthesis of poly(p‐phenylene methylene) (PPM)‐based block copolymers such as poly(p‐phenylene methylene)‐b‐poly(ε‐caprolactone) and poly(p‐phenylene methylene)‐b‐polytetrahydrofuran by mechanistic transformation was described. First, precursor PPM was synthesized by acid‐catalyzed polymerization of tribenzylborate at 16 °C. Then, this polymer was used as macroinitiators in either ring‐opening polymerization of ε‐caprolactone or cationic ring‐opening polymerization of tetrahydrofuran to yield respective block copolymers. The structures of the prepolymer and block copolymers were characterized by GPC and ¹H NMR investigations. The composition of block copolymers as determined by ¹H NMR and TGA analysis was found to be in very good agreement. The thermal behavior and surface morphology of the copolymers were also investigated, respectively, by differential scanning calorimetry and atomic force microscopy measurements, and the contribution of the major soft segment has been observed. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Synthesis and self‐assembly of diblock copolymers composed of poly(3‐hexylthiophene) and poly(fluorooctyl methacrylate) segments

Regioregular poly(3‐hexylthiophene)‐b‐poly(1H,1H‐dihydro perfluorooctyl methacrylate) (P3HT‐b‐PFOMA) diblock copolymers were synthesized by atom transfer radical polymerization of fluorooctyl methacrylate using bromoester terminated poly(3‐hexylthiophene) macroinitiators in order to investigate their morphological properties. The P3HT macroinitiator was previously prepared by chemical modification of hydroxy terminated P3HT. The block copolymers were well characterized by ¹H NMR spectroscopy and gel permeation chromatography. Transmission electron microscopy was used to investigate the nanostructured morphology of the diblock copolymers. The block copolymers are able to undergo microphase separation and self‐assemble into well‐defined and organized nanofibrillar‐like micellar morphology. The development of the morphology of P3HT‐b‐PFOMA block copolymers was investigated after annealing in solvent vapor and also in supercritical CO₂. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Synthesis of poly(vinylidene fluoride)‐b‐poly(styrene sulfonate) block copolymers by controlled radical polymerizations

Block copolymers based on poly(vinylidene fluoride), PVDF, and a series of poly(aromatic sulfonate) sequences were synthesized from controlled radical polymerizations (CRPs). According to the aromatic monomers, appropriate techniques of CRP were chosen: either iodine transfer polymerization (ITP) or atom transfer radical polymerization (ATRP) from PVDF‐I macromolecular chain transfer agents (CTAs) or PVDF‐CCl₃ macroinitiator, respectively. These precursors were produced either by ITP of VDF with C₆F₁₃I or by radical telomerization of VDF with chloroform, respectively. Poly(vinylidene fluoride)‐b‐poly(sodium styrene sulfonate), PVDF‐b‐PSSS, block copolymers were produced from both techniques via a direct polymerization of sodium styrene sulfonate (SSS) monomer or an indirect way with the use of styrene sulfonate ethyl ester (SSE) as a protected monomer. Although the reaction led to block copolymers, the kinetics of ITP of SSS showed that PVDF‐I macromolecular CTAs were not totally efficient because a limitation of the CTA consumption (56%) was observed. This was probably explained by both the low activity of the CTA (that contained inefficient PVDF‐CF₂CH₂? I) and a fast propagation rate of the monomer. That behavior was also noted in the ITP of SSE. On the other hand, ATRP of SSS initiated by PVDF‐CCl₃ was more controlled up to 50% of conversion leading to PVDF‐b‐PSSS block copolymer with an average number molar mass of 6000 g·mol^?1. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Synthesis of biocompatible and biodegradable block copolymers of polyvinyl alcohol‐block‐poly(ε‐caprolactone) using metal‐free living cationic polymerization

Applications of metal‐free living cationic polymerization of vinyl ethers using HCl · Et₂O are reported. Product of poly(vinyl ether)s possessing functional end groups such as hydroxyethyl groups with predicted molecular weights was used as a macroinitiator in activated monomer cationic polymerization of ε‐caprolactone (CL) with HCl · Et₂O as a ring‐opening polymerization. This combination method is a metal‐free polymerization using HCl · Et₂O. The formation of poly(isobutyl vinyl ether)‐b‐poly(ε‐caprolactone) (PIBVE‐b‐PCL) and poly(tert‐butyl vinyl ether)‐b‐poly(ε‐caprolactone) (PTBVE‐b‐PCL) from two vinyl ethers and CL was successful. Therefore, we synthesized novel amphiphilic, biocompatible, and biodegradable block copolymers comprised polyvinyl alcohol and PCL, namely PVA‐b‐PCL by transformation of acid hydrolysis of tert‐butoxy moiety of PTBVE in PTBVE‐b‐PCL. The synthesized copolymers showed well‐defined structure and narrow molecular weight distribution. The structure of resulting block copolymers was confirmed by ¹H NMR, size exclusion chromatography, and differential scanning calorimetry. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5169–5179, 2009     

Synthesis of novel tetrahydrofuran‐epichlorohydrin [poly(THF‐b‐ECH)] macromonomeric peroxy initiators by cationic copolymerization and the quantum chemically investigation of initiation system effects

Cationic polymerization of tetrahydrofuran (THF) and epichlorohydrin (ECH) was performed with peroxy initiators synthesized from bis (4,4′‐bromomethyl benzoyl peroxide (BBP) or bromomethyl benzoyl t‐butyl peroxy ester (t‐BuBP) and AgSbF₆ or ZnCl₂ system at 0 °C to obtain the poly(THF‐b‐ECH) macromonomeric peroxy initiators. Kinetic studies were accomplished for poly(THF‐b‐ECH) initiators. Poly(THF‐b‐ECH‐b‐MMA) and poly(THF‐b‐ECH‐b‐S) block copolymers were synthesized by bulk polymerization of methyl methacrylate (MMA) and styrene (S) with poly(THF‐b‐ECH) initiators. The quantum chemical calculations for the block copolymers, the initiating systems of the cationic polymerization of THF and ECH were achieved using HYPERCHEM 7.5 program. The optimized geometries of the polymers were investigated with the quantum chemical calculations. Poly(THF‐b‐ECH) initiators having peroxygen groups were used for graft copolymerization of polybutadien (PBd) to obtain poly(THF‐b‐ECH‐g‐PBd) crosslinked graft copolymers. The graft copolymers were investigated by sol‐gel analysis. Swelling ratio values of the graft copolymers in CHCl₃ were calculated. The characterizations of the polymers were achieved by FTIR, ¹H NMR, GPC, SEM, TEM, and DSC techniques. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2896–2909, 2010     

Synthesis of amphiphilic cationic copolymers poly[2‐(methacryloyloxy)ethyl trimethylammonium chloride‐co‐stearyl methacrylate] and their self‐assembly behavior in water and water‐ethanol mixtures

A series of amphiphilic cationic random copolymers, namely poly[2‐(methacryloyloxy)ethyl trimethylammonium chloride‐co‐stearyl methacrylate] or poly(MADQUAT‐co‐SMA), have been synthesized via conventional free‐radical copolymerization using 2,2′‐azobisisobutyronitrile (AIBN) as initiator and n‐dodecanethiol as chain transfer agent. The resultant products were then characterized by FT‐IR, ¹H NMR, MALDI‐TOF MS measurements. From the number‐average molecular weights of the copolymers, we can conclude that these copolymers have oligomeric structure with a limited number of hydrophilic and hydrophobic moieties in a short polymer chain. The reactivity ratios (r_MADQUAT = 0.83, r_SMA = 0.25) between the hydrophilic MADQUAT monomer and the hydrophobic SMA monomer were calculated by the Finemann and Ross method, which was based on the results of ¹H NMR analysis. The surface activity of the random copolymers was studied by the combination of surface tension and contact angle measurement, and the results indicated that these copolymers possess relatively high surface activity. The critical aggregation concentrations (cac) of the copolymers in aqueous solution were determined by fluorescence probe method as well as surface tension measurement. The different nanoparticles of poly(MADQUAT‐co‐SMA) copolymers formed in pure water or ethanol‐water mixture were proved by the particle size and size distribution in the measurement of dynamic light scattering (DLS). Furthermore, using transmission electron microscopy (TEM), we could observe various self‐assembly morphologies of these random copolymer. All these results show that the amphiphilic cationic random copolymers have a good self‐assembly behavior, even if they are ill‐defined copolymers. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4670–4684, 2009     

Controlled synthesis of amphiphilic block copolymers based on poly(isobutylene) macromonomers

The synthesis of a monoacrylate functionalized poly(isobutylene) (PIB) macromonomer (PIBA) has been achieved by a two‐step reaction starting from a commercially available PIB. Firstly, terminal olefins (vinylidene and trisubstituted olefin) of PIB were transformed to a phenolic residue by Friedel‐Crafts alkylation followed by subsequent esterification of the phenol with acryloyl chloride, catalyzed by triethylamine. PIBA structure was confirmed by ¹H‐NMR, ¹³C‐NMR and GPC before utilizing in the RAFT copolymerization with N,N‐dimethylacrylamide (DMA) to obtain statistical copolymers (P[(DMA‐co‐(PIBA)]). Monomer conversions were consistently higher than 85% for both DMA and PIBA as monomer feed composition was varied. Chain extension of poly(N,N‐dimethylacrylamide) with PIBA to synthesize block copolymers (P[(DMA‐b‐(PIBA)]) was also achieved with near quantitative monomer conversions (>97%). Block formation efficiency was not quantitative but purification of block copolymers was possible by selective precipitation. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 634–643     

Iodine-Transfer Polymerization (ITP) of Ethylene and Copolymerization with Vinyl Acetate

Controlled radical polymerization of ethylene using different commercially available, cheap, and non-toxic iodo alkyls is performed by iodine transfer polymerization (ITP) under mild conditions (≤100 °C and ≤200 bar). The formed well-defined iodo end-capped polyethylene (PE−I) species is very stable upon storage. Narrow molar-mass distributions (dispersities around 1.6) were obtained up to number average molar masses of 7300 g mol⁻¹. The ethylene copolymerization by ITP (ITcoP) with vinyl acetate allowed to form a broad range of poly(ethylene-co-vinyl acetate) (EVA) containing from 0 to 85 mol % of VAc unit. In addition, EVA-b-PE block copolymers or EVA-b-EVA gradient block copolymers with different content of VAc in the blocks were obtained for the first time using ITP. Finally, reactivity trends were explored by a theoretical mechanistic study. This highly versatile synthetic platform provides a straightforward access to a diverse range of well-defined PE based polymer materials.     

ATRP of methyl methacrylate initiated with a bifunctional initiator bearing bromomethyl functional groups: Synthesis of the block and graft copolymers

This article reports the synthesis of the block and graft copolymers using peroxygen‐containing poly(methyl methacrylate) (poly‐MMA) as a macroinitiator that was prepared from the atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) in the presence of bis(4,4′‐bromomethyl benzoyl peroxide) (BBP). The effects of reaction temperatures on the ATRP system were studied in detail. Kinetic studies were carried out to investigate controlled ATRP for BBP/CuBr/bpy initiating system with MMA at 40 °C and free radical polymerization of styrene (S) at 80 °C. The plots of ln ([M_o]/[M_t]) versus reaction time are linear, corresponding to first‐order kinetics. Poly‐MMA initiators were used in the bulk polymerization of S to obtain poly (MMA‐b‐S) block copolymers. Poly‐MMA initiators containing undecomposed peroygen groups were used for the graft copolymerization of polybutadiene (PBd) and natural rubber (RSS‐3) to obtain crosslinked poly (MMA‐g‐PBd) and poly(MMA‐g‐RSS‐3) graft copolymers. Swelling ratio values (q_v) of the graft copolymers in CHCl₃ were calculated. The characterizations of the polymers were achieved by Fourier‐transform infrared spectroscopy (FTIR), ¹H‐nuclear magnetic resonance (¹H NMR), gel‐permeation chromatography (GPC), differential scanning calorimetry (DSC), thermogravimetric analysis, scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), and the fractional precipitation (γ) techniques. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1364–1373, 2010     

Novel synthesis of biodegradable linear and star block copolymers based on ε‐caprolactone and lactides using potassium‐based catalyst

Biodegradable, triblock poly(lactide)‐block‐poly(ε‐caprolactone)‐block‐poly(lactide) (PLA‐b‐PCL‐b‐PLA) copolymers and 3‐star‐(PCL‐b‐PLA) block copolymers were synthesized by ring opening polymerization of lactides in the presence of poly(ε‐caprolactone) diol or 3‐star‐poly(ε‐caprolactone) triol as macroinitiator and potassium hexamethyldisilazide as a catalyst. Polymerizations were carried out in toluene at room temperature to yield monomodal polymers of controlled molecular weight. The chemical structure of the copolymers was investigated by ¹H and ¹³C‐NMR. The formation of block copolymers was confirmed by NMR and DSC investigations. The effects of copolymer composition and molecular structure on the physical properties were investigated by GPC and DSC. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5363–5370, 2008     

Micelle formation and sol–gel transition behavior of comb‐like amphiphilic poly((PLGA‐b‐PEG)MA) copolymers

Comb‐like amphiphilic poly(poly((lactic acid‐co‐glycolic acid)‐block‐poly(ethylene glycol)) methacrylate (poly((PLGA‐b‐PEG)MA)) copolymers were synthesized by radical polymerization. (PLGA‐b‐PEG)MA macromonomer was prepared by ring‐opening bulk polymerization of DL ‐lactide and glycolide using purified poly(ethylene glycol) monomethacrylate (PEGMA) as an initiator. (PLGA‐b‐PEG)MA macromonomer was copolymerized with PEGMA and/or acrylic acid (AA) by radical polymerization to produce comb‐like amphiphilic block copolymers. The molecular weight and chemical structure were investigated by GPC and ¹H NMR. Poly((PLGA‐b‐PEG)MA) copolymer aqueous solutions showed gel–sol transition behavior with increasing temperature, and gel‐to‐sol transition temperature decreased as the compositions of the hydrophilic PEGMA and AA increased. The gel‐to‐sol transition temperature of the terpolymers of the poly((PLGA‐b‐PEG)MA‐co‐PEGMA‐co‐AA) also decreased when the pH was increased. The effective micelle diameter obtained from dynamic light scattering increased with increasing temperature and with increasing pH. The critical micelle concentration increased as the composition of the hydrophilic monomer component, PEGMA and AA, were increased. The spherical shape of the hyperbranched polymers in aqueous environment was observed by atomic force microscopy. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1954–1963, 2008     

Fluorinated block copolymers containing poly(vinylidene fluoride) or poly(vinylidene fluoride‐co‐hexafluoropropylene) blocks from perfluoropolyethers: Synthesis and thermal properties

PFPE‐b‐PVDF and PFPE‐b‐poly(VDF‐co‐HFP) block copolymers [where PFPE, PVDF, VDF, and HFP represent perfluoropolyether, poly(vinylidene fluoride), vinylidene fluoride (or 1,1‐difluoroethylene), and hexafluoropropylene] were synthesized by radical (co)telomerizations of VDF (or VDF and HFP) with an iodine‐terminated perfluoropolyether (PFPE‐I). Di‐tert‐butyl peroxide (DTBP) was used and was shown to act as an efficient thermal initiator. The numbers of VDF and VDF/HFP base units in the block copolymers were assessed with ¹⁹F NMR spectroscopy. According to the initial [PFPE‐I]₀/[fluoroalkenes]₀ and [DTBP]₀/[fluoroalkenes]₀ molar ratios, fluorinated block copolymers of various molecular weights (1500–30,300) were obtained. The states and thermal properties of these fluorocopolymers were investigated. The compounds containing PVDF blocks with more than 30 VDF units were crystalline, whereas all those containing poly(VDF‐co‐HFP) blocks exhibited amorphous states, whatever the numbers were of the fluorinated base units. All the samples showed negative glass‐transition temperatures higher than that of the starting PFPE. Interestingly, these PFPE‐b‐PVDF and PFPE‐b‐poly(VDF‐co‐HFP) block copolymers exhibited good thermostability. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 160–171, 2003     

Synthesis of poly(n‐hexyl isocyanate‐b‐N‐vinylpyrrolidone) block copolymers by the combination of anionic and nitroxide‐mediated radical polymerizations: Micellization properties in aqueous solutions

A combination of anionic and nitroxide‐mediated radical polymerizations (dual initiator) was employed for the synthesis of poly(n‐hexyl isocyanate‐b‐N‐vinylpyrrolidone) (PHIC‐b‐PNVP) block copolymers. The samples were characterized with a size exclusion chromatograph equipped with refractive‐index and light scattering detectors as well as ¹H NMR spectroscopy. Relatively good control over the molecular weights was achieved. However, rather broad molecular weight distributions were obtained. The micellar properties of the PHIC‐b‐PNVP block copolymers were studied in water, which is a selective solvent for the poly(N‐vinylpyrrolidone) blocks. Static and dynamic light scattering revealed the presence of equilibrium between the micelles and clusters. The clusters partially deaggregated with increasing temperature. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5719–5728, 2006     

Well‐defined polyolefin/poly(ε‐caprolactone) diblock copolymers: New synthetic strategy and application

A new synthetic strategy, the combination of living polymerization of ylides and ring‐opening polymerization (ROP), was successfully used to obtain well‐defined polymethylene‐b‐poly(ε‐caprolactone) (PM‐b‐PCL) diblock copolymers. Two hydroxyl‐terminated polymethylenes (PM‐OH, M_n= 1800 g mol^?1 (PDI = 1.18) and M_n = 6400 g mol^?1 (PDI = 1.14)) were prepared using living polymerization of dimethylsulfoxonium methylides. Then, such polymers were successfully transformed to PM‐b‐PCL diblock copolymers by using stannous octoate as a catalyst for ROP of ε‐caprolactone. The GPC traces and ¹H NMR of PM‐b‐PCL diblock copolymers indicated the successful extension of PCL segment (M_n of PM‐b‐PCL = 5200–10,300 g mol^?1; PDI = 1.06–1.13). The thermal properties of the double crystalline diblock copolymers were investigated by differential scanning calorimetry (DSC). The results indicated that the incorporation of crystalline segments of PCL chain effectively influence the crystalline process of PM segments. The low‐density polyethylene (LDPE)/PCL and LDPE/polycarbonate (PC) blends were prepared using PM‐b‐PCL as compatibilizer, respectively. The scanning electron microscopy (SEM) observation on the cryofractured surface of such blend polymers indicates that the PM‐b‐PCL diblock copolymers are effective compatibilizers for LDPE/PCL and LDPE/PC blends. Porous films were fabricated via the breath‐figure method using different concentration of PM‐b‐PCL diblock copolymers in CH₂Cl₂ under a static humid condition. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Controlled random and alternating copolymerization of (meth)acrylates,acrylonitrile, and (meth)acrylamides with vinyl ethers by organotellurium‐, organostibine‐, and organobismuthine‐mediated living radical polymerization reactions

Random and alternating copolymerizations of acrylates, methacrylates, acrylonitorile, and acrylamides with vinyl ethers under organotellurium‐, organostibine‐, and organobismuthine‐mediated living radical polymerization (TERP, SBRP, and BIRP, respectively) have been studied. Structurally well‐controlled random and alternating copolymers with controlled molecular weights and polydispersities were synthesized. The highly alternating copolymerization occurred in a combination of acrylates and vinyl ethers and acrylonitorile and vinyl ethers by using excess amount of vinyl ethers over acrylates and acrylonitorile. On the contrary, alternating copolymerization did not occur in a combination of acrylamides and vinyl ethers even excess amount of vinyl ethers were used. The reactivity of polymer‐end radicals to a vinyl ether was estimated by the theoretical calculations, and it was suggested that the energy level of singly occupied molecular orbital (SOMO) of polymer‐end radical species determined the reactivity. By combining living random and alternating copolymerization with living radical or living cationic polymerization, new block copolymers, such as (PBA‐alt‐PIBVE)‐block‐(PtBA‐co‐PIBVE), PBA‐block‐(PBA‐alt‐PIBVE), and (PTFEA‐alt‐PIBVE)‐block‐PIBVE, with controlled macromolecular structures were successfully synthesized. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Sequence‐controlled cationic ring‐opening copolymerization of spiroorthocarbonate and oxetane

Pseudo block and triblock copolymers were synthesized by the cationic ring‐opening copolymerization of 1,5,7,11‐tetraoxaspiro[5.5]undecane (SOC1) with trimethylene oxide (OX) via one‐shot and two‐shot procedures, respectively. When SOC1 and OX were copolymerized cationically with boron trifluoride etherate (BF₃OEt₂) as an initiator in CH₂Cl₂ at 25 °C, OX was consumed faster than SOC1. SOC1 was polymerized from the OX‐rich gradient copolymer produced in the initial stage of the copolymerization to afford the corresponding pseudo block copolymer, poly [(OX‐grad‐SOC1)‐b‐SOC1]. We also succeeded in the synthesis of a pseudo triblock copolymer by the addition of OX during the course of the polymerization of SOC1 before its complete consumption, which provided the corresponding pseudo triblock copolymer, poly[SOC1‐b‐(OX‐grad‐SOC1)‐b‐SOC1]. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3233–3241, 2006     

Three‐arm star block copolymers of ε‐caprolactone and acrylic acid: Synthesis and micellization behavior

A series of well‐defined three‐arm star poly(ε‐caprolactone)‐b‐poly(acrylic acid) copolymers having different block lengths were synthesized via the combination of ring‐opening polymerization (ROP) and atom transfer radical polymerization (ATRP). First, three‐arm star poly(ε‐caprolactone) (PCL) (M_n = 2490–7830 g mol^?1; M_w/M_n = 1.19–1.24) were synthesized via ROP of ε‐caprolactone (ε‐CL) using tris(2‐hydroxyethyl)cynuric acid as three‐arm initiator and stannous octoate (Sn(Oct)₂) as a catalyst. Subsequently, the three‐arm macroinitiator transformed from such PCL in high conversion initiated ATRPs of tert‐butyl acrylate (^tBuA) to construct three‐arm star PCL‐b‐P^tBuA copolymers (M_n = 10,900–19,570 g mol^?1; M_w/M_n = 1.14–1.23). Finally, the three‐arm star PCL‐b‐PAA copolymer was obtained via the hydrolysis of the PtBuA segment in three‐arm star PCL‐b‐P^tBuA copolymers. The chain structures of all the polymers were characterized by gel permeation chromatography, proton nuclear magnetic resonance (¹H NMR), and Fourier transform infrared spectroscopy. The aggregates of three‐arm star PCL‐b‐PAA copolymer were studied by the determination of critical micelles concentration and transmission electron microscope. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Synthesis and morphology of polyethylene‐block‐poly(methyl methacrylate) through the combination of metallocene catalysis with living radical polymerization

Polyethylene‐block‐poly(methyl methacrylate) (PE‐b‐PMMA) was successfully synthesized through the combination of metallocene catalysis with living radical polymerization. Terminally hydroxylated polyethylene, prepared by ethylene/allyl alcohol copolymerization with a specific zirconium metallocene/methylaluminoxane/triethylaluminum catalyst system, was treated with 2‐bromoisobutyryl bromide to produce terminally esterified polyethylene (PE‐Br). With the resulting PE‐Br as an initiator for transition‐metal‐mediated living radical polymerization, methyl methacrylate polymerization was subsequently performed with CuBr or RuCl₂(PPh₃)₃ as a catalyst. Then, PE‐b‐PMMA block copolymers of different poly(methyl methacrylate) (PMMA) contents were prepared. Transmission electron microscopy of the obtained block copolymers revealed unique morphological features that depended on the content of the PMMA segment. The block copolymer possessing 75 wt % PMMA contained 50–100‐nm spherical polyethylene lamellae uniformly dispersed in the PMMA matrix. Moreover, the PE‐b‐PMMA block copolymers effectively compatibilized homopolyethylene and homo‐PMMA at a nanometer level. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3965–3973, 2003     

Perfluorocarbon‐loaded shell crosslinked knedel‐like nanoparticles: Lessons regarding polymer mobility and self‐assembly

Reversible addition‐fragmentation chain transfer polymerization was employed to synthesize a set of copolymers of styrene (PS) and 2,3,4,5,6‐pentafluorostyrene (PPFS), as well as block copolymers with tert‐butyl acrylate (PtBA)‐b‐PS‐co‐PPFS, with control over molecular weight and polydispersity. It was found that the copolymerization of styrene and PFS allowed for the preparation of gradient copolymers with opposite levels of monomer consumption, depending on the feed ratio. Conversion to amphiphilic block copolymers, PAA‐b‐(PS‐co‐PPFS), by removing the protecting groups was followed by fitting with monomethoxy poly(ethylene glycol) chains. Solution‐state assembly and intramicellar crosslinking afforded shell crosslinked knedel‐like (SCK) block copolymer nanoparticles. These fluorinated nanoparticles (ca. 20 nm diameters) were studied as potential magnetic resonance imaging (MRI) contrast agents based on the ¹⁹F‐nuclei; however, it was found that packaging of the hydrophobic fluorinated polymers into the core domain restricted the mobility of the chains and prohibited ¹⁹F NMR spectroscopy when the particles were dispersed in water without an organic cosolvent. Packing of perflouro‐15‐crown‐5‐ether (PFCE) into the polymer micelle was demonstrated with good uptake efficiency; however, it was necessary to swell the core with a good solvent (DMSO) to increase the mobility and observe the ¹⁹F NMR signal of the PFCE. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1023–1037, 2009     

Synthesis and characterization of liquid‐crystalline block copolymers with cyanoterphenyl moieties by atom transfer radical polymerization

A series of new mesomorphic block copolymers composedofdifferentmacroinitiators, including poly(ethylene oxide), polystyrene, and poly(ethylene oxide)‐b‐polystyrene,and polymethacrylate with a pendent cyanoterphenyl group were synthesized through atom transfer radical polymerization. The number‐average molecular weights of the three diblock copolymers, determined by gel permeation chromatography, were 10,254, 9,772, and 15,632 g mol^?1, and their polydispersity indices were 1.17, 1.28, and 1.34. The mesomorphic and optical properties of all the block copolymers were investigated, and they possessed a smectic A phase with mesophasic ranges wider than 100 °C. Moreover, X‐ray diffraction patterns provided evidence of the smectic A phase and the corresponding interdigitated packing of all the polymers. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4593–4602, 2006