Aqueous solution properties of pH‐responsive AB diblock acrylamido–styrenic copolymers synthesized via aqueous reversible addition–fragmentation chain transfer

Here we report the synthesis and solution characterization of a novel series of AB diblock copolymers with neutral, water‐soluble A blocks consisting of N,N‐dimethylacrylamide and pH‐responsive B blocks of N,N‐dimethylvinylbenzylamine. To our knowledge, this represents the first example of an acrylamido–styrenic block copolymer prepared directly in a homogeneous aqueous solution. The best blocking order [with poly(N,N‐dimethylacrylamide) as a macro‐chain‐transfer agent] yielded well‐defined block copolymers with minimal homopolymer impurities. The reversible aggregation of these block copolymers in aqueous media was studied with ¹H NMR spectroscopy and dynamic light scattering. Finally, an example of core‐crosslinked micelles was demonstrated by the addition of a difunctional crosslinking agent to a micellar solution of the parent block copolymer. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1724–1734, 2004     

Synthesis and characterization of multiblock copolymers composed of poly(5‐methyl‐5‐benzyloxycarbonyl‐1,3‐dioxan‐2‐one) outer blocks and poly(L‐lactide) inner blocks

Ethylene glycol (EG) initiated, hydroxyl‐telechelic poly(L ‐lactide) (PLLA) was employed as a macroinitiator in the presence of a stannous octoate catalyst in the ring‐opening polymerization of 5‐methyl‐5‐benzyloxycarbonyl‐1,3‐dioxan‐2‐one (MBC) with the goal of creating A–B–A‐type block copolymers having polycarbonate outer blocks and a polyester center block. Because of transesterification reactions involving the PLLA block, multiblock copolymers of the A–(B–A)_n–B–A type were actually obtained, where A is poly(5‐methyl‐5‐benzyloxycarbonyl‐1,3‐dioxan‐2‐one), B is PLLA, and n is greater than 0. ¹H and ¹³C NMR spectroscopy of the product copolymers yielded evidence of the multiblock structure and provided the lactide sequence length. For a PLLA macroinitiator with a number‐average molecular weight of 2500 g/mol, the product block copolymer had an n value of 0.8 and an average lactide sequence length (consecutive C₆H₈O₄ units uninterrupted by either an EG or MBC unit) of 6.1. For a PLLA macroinitiator with a number‐average molecular weight of 14,400 g/mol, n was 18, and the average lactide sequence length was 5.0. Additional evidence of the block copolymer architecture was revealed through the retention of PLLA crystallinity as measured by differential scanning calorimetry and wide‐angle X‐ray diffraction. Multiblock copolymers with PLLA crystallinity could be achieved only with isolated PLLA macroinitiators; sequential addition of MBC to high‐conversion L ‐lactide polymerizations resulted in excessive randomization, presumably because of residual L ‐lactide monomer. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6817–6835, 2006     

Synthesis and properties of novel polyimide/nylon‐6 triblock copolymers

Nylon‐6‐b‐polyimide‐b‐nylon‐6 copolymers were prepared by first synthesizing a series of imide oligomers end‐capped with phenyl 4‐aminobenzoate. The oligomers were then used to activate the anionic polymerization of molten ϵ‐caprolactam. In the block copolymer syntheses, the phenyl ester groups reacted quickly with caprolactam anions at 120 °C to generate N‐acyllactam moieties, which activated the anionic polymerization. In essence, nylon‐6 chains grew from the oligomer chain ends. All of the block copolymers had higher moduli and tensile strengths than those of nylon‐6. However, their elongations at break were much lower. The thermal stability, chemical resistance, moisture resistance, and impact strength were dramatically increased by the incorporation of only 5 wt % polyimide in the block copolymers. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 4247–4257, 2000     

Preparation of polymeric vesicles through ultrasonic treatment of poly(styrene‐block‐2‐vinylpyridine) micelles under alkaline conditions

An approach for the preparation of block copolymer vesicles through ultrasonic treatment of polystyrene‐block‐poly(2‐vinyl pyridine) (PS‐b‐P2VP) micelles under alkaline conditions is reported. PS‐b‐P2VP block copolymers in toluene, a selective solvent for PS, form spherical micelles. If a small amount of NaOH solution is added to the micelles solution during ultrasonic treatment, organic‐inorganic Janus‐like particles composed of the PS‐b‐P2VP block copolymers and NaOH are generated. After removal of NaOH, block copolymer vesicles are obtained. A possible mechanism for the morphological transition from spherical micelles to vesicles or Janus‐like particles is discussed. If the block copolymer micelles contain inorganic precursors, such as FeCl₃, hybrid vesicles are formed, which may be useful as biological and chemical sensors or nanostructured templates. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014 , 52, 953–959     

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     

Synthesis and characterization of well‐defined block and statistical copolymers based on lauryl methacrylate and 2‐(acetoacetoxy)ethyl methacrylate using RAFT‐controlled radical polymerization

Four well‐defined diblock copolymers and one statistical copolymer based on lauryl methacrylate (LauMA) and 2‐(acetoacetoxy)ethyl methacrylate (AEMA) were prepared using reversible addition‐fragmentation chain transfer (RAFT) polymerization. The polymers were characterized in terms of molecular weights, polydispersity indices (ranging between 1.12 and 1.23) and compositions by size exclusion chromatography and ¹H NMR spectroscopy, respectively. The preparation of the block copolymers was accomplished following a two‐step methodology: First, well‐defined LauMA homopolymers were prepared by RAFT using cumyl dithiobenzoate as the chain transfer agent (CTA). Kinetic studies revealed that the polymerization of LauMA followed first‐order kinetics demonstrating the “livingness” of the RAFT process. The pLauMAs were subsequently used as macro‐CTA for the polymerization of AEMA. The glass transition (T_g) and decomposition temperatures (ranging between 200 and 300 °C) of the copolymers were determined using differential scanning calorimetry and thermal gravimetric analysis, respectively. The T_gs of the LauMA homopolymers were found to be around ?53 °C. Block copolymers exhibited two T_gs suggesting microphase separation in the bulk whereas the statistical copolymer presented a single T_g as expected. Furthermore, the micellization behavior of pLauMA‐b‐pAEMA block copolymers was investigated in n‐hexane, a selective solvent for the LauMA block, using dynamic light scattering. pLauMA‐b‐pAEMA block copolymers formed spherical micelles in dilute hexane solutions with hydrodynamic diameters ranging between 30 and 50 nm. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5442–5451, 2008     

Architecture‐controlled synthesis of redox‐degradable hyperbranched polyglycerol block copolymers and the structural implications of their degradation

We have successfully synthesized a series of redox‐degradable hyperbranched polyglycerols using a disulfide containing monomer, 2‐((2‐(oxiran‐2‐ylmethoxy)ethyl)disulfanyl) ethan‐1‐ol (SSG), to yield PSSG homopolymers and hyperbranched block copolymers, P(G‐b‐SSG) and P(SSG‐b‐G), containing nondegradable glycerol (G) monomers. Using these polymers, we have explored the structures of the hyperbranched block copolymers and their related degradation products. Furthermore, side reaction such as reduction of disulfide bond during the polymerization was investigated by employing the free thiol titration experiments. We elucidated the structures of the degradation products with respect to the architecture of the hyperbranched block copolymer under redox conditions using ¹H NMR and GPC measurements. For example, the degradation products of P(G‐b‐SSG) and P(SSG‐b‐G) are clearly different, demonstrating the clear distinction between linear and hyperbranched block copolymers. We anticipate that this study will extend the structural diversity of PG based polymers and aid the understanding of the structures of degradable hyperbranched PG systems. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1752–1761     

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 block copolymers from 2‐vinylnaphthalene by anionic polymerization

The anionic polymerization of 2‐vinylnaphthalene (2VN) has been studied in tetrahydrofuran (THF) at ?78 °C and in toluene at 40 °C. 2VN polymerization in THF, toluene, or toluene/THF (99:1 v/v) initiated by sec‐butyllithium (sBuLi) indicates living characteristics, affording polymers with predefined molecular weights and narrow molecular weight distributions. Block copolymers of 2VN with methyl methacrylate (MMA) and tert‐butyl acrylate (tBA) have been synthesized successfully by sequential monomer addition in THF at ?78 °C initiated by an adduct of sBuLi–LiCl. The crossover propagation from poly(2‐vinylnaphthyllithium) (P2VN) macroanions to MMA and tBA appears to be living, the molecular weight and composition can be predicted, and the molecular weight distribution of the resulting block copolymer is narrow (weight‐average molecular/number‐average molecular weight < 1.3). Block copolymers with different chain lengths for the P2VN segment can easily be prepared by variations in the monomer ratios. The block copolymerization of 2VN with hexamethylcyclotrisiloxane also results in a block copolymer of P2VN and poly(dimethylsiloxane) (PDMS) contaminated with a significant amount of homo‐PDMS. Poly(2VN‐b‐nBA) (where nBA is n‐butyl acrylate) has also been prepared by the transesterification reaction of the poly(2VN‐b‐tBA) block copolymer. Size exclusion chromatography, Fourier transform infrared, and ¹H NMR measurements indicate that the resulting polymers have the required architecture. The corresponding amphiphilic block copolymer of poly(2VN‐b‐AA) (where AA is acrylic acid) has been synthesized by acidic hydrolysis of the ester group of tert‐butyl from the poly(2VN‐b‐tBA) copolymer. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4387–4397, 2002     

Block copolymerization of tert‐butyl methacrylate with α,ω‐difunctionalized polystyrene macroiniferter and hydrolysis to amphiphilic block copolymer

The block copolymerization of tert‐butyl methacrylate (tBMA) with a difunctionalized polystyrene (PS) macroinitiator was investigated. The polymerizations were performed under UV light irradiation using PS bearing α‐ and ω‐functionalized end groups containing diethyldithiocarbamyl groups as a macroiniferter. Kinetic studies indicate the molecular weights of triblock copolymers increased linearly with the conversion. Block copolymers with different lengths of PtBMA segments were easily prepared by varying the ratio of tBMA and PS macroiniferter or by controlling the monomer conversion. The formations of block copolymers were characterized by gel permeation chromatographic, ¹H NMR, and DSC analyses. PtBMA segments of the triblock copolymer were subsequently hydrolyzed quantitatively to poly(methacrylic acid) segments using concentrated HCl as a catalyst in a refluxing solution of dioxane, and then an amphiphilic ABA triblock copolymer was produced. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1450–1455, 2001     

Recent advances in the solution self‐assembly of amphiphilic “rod‐coil” copolymers

Solution self‐assembly of amphiphilic “rod‐coil” copolymers, especially linear block copolymers and graft copolymers (also referred to as polymer brushes), has attracted considerable interest, as replacing one of the blocks of a coil‐coil copolymer with a rigid segment results in distinct self‐assembly features compared with those of the coil‐coil copolymer. The unique interplay between microphase separation of the rod and coil blocks with great geometric disparities can lead to the formation of unusual morphologies that are distinctly different from those known for coil‐coil copolymers. This review presents the recent achievements in the controlled self‐assembly of rod‐coil linear block copolymers and graft copolymers in solution, focusing on copolymer systems containing conjugated polymers, liquid crystalline polymers, polypeptides, and polyisocyanates as the rod segments. The discussions concentrate on the principle of controlling over the morphology of rod‐coil copolymer assemblies, as well as their distinctive optical and optoelectronic properties or biocompatibility and stimuli‐responsiveness, which afford the assemblies great potential as functional materials particularly for optical, optoelectronic and biological applications. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 1459–1477     

Combining atom‐transfer radical polymerization and ring‐opening polymerization through bifunctional initiators derived from hydroxy benzyl alcohol—Preparation and characterization of initiators,macroinitiators, and block copolymers

A simple, one‐step procedure has been developed for the preparation of bifunctional initiators capable of polymerizing monomers suitable for atom‐transfer radical polymerization (ATRP) and ring‐opening polymerization (ROP). These bifunctional initiators were employed for making narrow disperse poly(styrene) macroinitiators, which were subsequently used for the ROP of various lactides to yield poly(styrene‐block‐lactide) copolymers. Thermogravimetric analysis (TGA) of these block copolymers are interesting in that it shows a two‐step degradation curve with the first step corresponding to the degradation of poly(lactide) segment and the second step associated with the poly(styrene) segment of the block copolymer. This nature of the block copolymer makes it possible to estimate the block copolymer content by TGA in addition to the ¹H NMR spectroscopic analysis. Thus, this study for the first time highlights the possibility of making porous materials by thermal means which are otherwise obtained by base hydrolysis. The bifunctional initiators were prepared by the esterification of 3‐hydroxy, 4‐hydroxy, and 3,5‐dihydroxy benzyl alcohols with α‐bromoisobutyryl bromide and 2‐bromobutyryl bromide. A mixture of products was obtained, which were purified by column chromatography. The esterified benzyl alcohols were employed in the polymerization of styrene under copper (Cu)‐catalyzed ATRP conditions to yield macroinitiators with low polydispersity. These macroinitiators were subsequently used in the ROP of L ‐, DL ‐, and mixture of lactides. The formation of block copolymers was confirmed by gel permeation chromatography (GPC), spectroscopic and thermal characterizations. The molecular weight of the block copolymers was always higher than the macroinitiator, and the GPC chromatogram was symmetrical indicating the uniform initiation of ROP by the macroinitiators. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 102–116, 2008     

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     

Poly(3‐hexyl thiophene)‐b‐poly(N‐isopropyl acrylamide): Synthesis and its composition dependent structural,solubility, thermoresponsive,electrochemical, and electronic properties

Conjugated block copolymers consisting of poly(3‐hexyl thiophene) (P3HT) and a thermoresponsive polymer poly(N‐isopropyl acrylamide) (PNIPAM) with varying composition have been synthesized by facile click reaction between alkyne terminated P3HT and azide terminated PNIPAM. The composition‐dependent solubility, thermoresponsive property in water, phase behavior, electrochemical, optical, and electronic properties of the block copolymers were systematically investigated. The block copolymers with higher volume fraction of PNIPAM form thermoresponsive spherical micelles with P3HT‐rich crystalline cores and PNIPAM coronas. Both X‐ray and atomic force microscopic studies indicated that the blocks copolymers showed well‐defined microphase separated nanostructures and the structure depended on the composition of the blocks. The electrochemical study of the block copolymers clearly demonstrated that the extent of charge transport through the block copolymer thin film was similar to P3HT homopolymer without any significant change in the band gap. The block copolymers showed improved or similar charge carrier mobility compared with the pure P3HT depending on the composition of the block copolymer. These P3HT‐b‐PNIPAM copolymers were interesting for fabrication of optoelectronic devices capable of thermal and moisture sensing as well as for studying the thermoresponsive colloidal structures of semiconductor amphiphilic systems. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1785–1794     

Synthesis and thermal,mechanical, and optical properties of A–B–A or A–B block copolymers containing poly(norbornene‐co‐1‐octene)

A–B–A block copolymers which consist of poly(norbornene‐co‐1‐octene) and atactic polypropylene (PP) segments were synthesized by using ansa‐fluorenylamidotitanium complex as a catalyst varying the ratio of norbornene, 1‐octene, and propylene. The copolymer was obtained quantitatively with high molecular weight (>100,000) and narrow molecular weight distribution (polydispersity index, <1.5). A–B block copolymers of poly(norbornene‐co‐1‐octene) and poly(methyl methacrylate) (PMMA) was also obtained by the same procedure. Mechanical and optical properties of these copolymer films, which were obtained by solution casting process, were also investigated. Introduction of PP soft segment greatly improved mechanical properties, keeping their high transparency. Introduction of PMMA block also increased the tensile strength. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 267–271     

Hydroxide‐ion transport and stability of diblock copolymers with a polydiallyldimethyl ammonium hydroxide block

Base‐stable amphiphilic diblock copolymers with a polydiallyl dimethyl ammonium hydroxide block were synthesized and characterized to quantify hydroxide‐ion transport in the hydrated state; polystyrene was the hydrophobic block. The challenge of synthesizing a copolymer comprising blocks with very different solubility behaviors was addressed by a combination of reversible addition fragmentation chain transfer polymerization and ion metathesis. Both monomers used in the polymerization are commercially available on industrial scales. Hydroxide‐ion conductivities of 0.8 mS/cm were achieved in hot‐pressed membranes immersed in water at room temperature despite relatively low water uptake (4.2 water molecules per hydroxide ion). The stability of the polydimethyl ammonium hydroxide chains was investigated in 2 M NaOD at 60 °C. ¹H NMR spectroscopy studies showed no detectable degradation after 2000 hours. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2243–2248     

Block and star block copolymers by mechanism transformation. II. Synthesis of poly(DOP‐b‐St) by combination of ATRP and CROP

Styrene underwent the ATRP process using an asymmetric difunctional initiator, 2‐hydroxylethyl 2′‐bromobutyrate in combination with CuBr and 2,2′‐bipyridine (bpy). Polystyrene with hydroxyl and bromine groups at each end of the polymer (HO‐PSt‐Br) was obtained, and used as a chain‐transfer agent in the cationic ring‐opening polymerization of 1,3‐dioxepane with triflic acid as initiator. The structures of the polymerization products were analyzed by ¹H NMR and GPC analyses, indicating the formation of block copolymer. The molecular weight distribution of the block copolymer was relatively narrow and the molecular weight of the polyDOP block was high. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 436–443, 2000     

Encapsulation and release by star‐shaped block copolymers as unimolecular nanocontainers

A five‐arm star‐shaped poly(ethylene oxide) (PEO) with terminal bromide groups was used as a macroinitiator for the atom transfer radical polymerization of tert‐butyl acrylate (tBA), resulting in five‐arm star‐shaped poly(ethylene oxide)‐block‐poly(tert‐butyl acrylate) block copolymers. The polymerization proceeded in a controlled way using a copper(I)bromide/pentamethyl diethylenetriamine catalytic system in acetonitrile as solvent. The hydrolysis of the tBA blocks of the amphiphilic star‐shaped PEO‐b‐PtBA block copolymer resulted in dihydrophilic star structures. The encapsulation of the star‐block copolymers and their release properties in acid environment have been followed by UV‐spectroscopy and color changes, using the dye methyl orange as a hydrophilic guest molecule. Characterization of the structures has been done by ¹H NMR, size exclusion chromatography, MALDI‐TOF, and differential scanning calorimetry. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 650–660, 2008     

Synthesis of end‐functionalized AB copolymers. II. Synthesis and characterization of carboxyl‐terminated poly(ethylene glycol)–poly(amino acid) block copolymers

AB block copolymers composed of hydrophilic poly(ethylene glycol) (PEG) and hydrophobic poly(amino acid) with a carboxyl group at the end of PEG were synthesized with α‐carboxylic sodium‐ω‐amino‐PEG as a macroinitiator for the ring‐opening polymerization of N‐carboxy anhydride. Characterizations by ¹H NMR, IR, and gel permeation chromatography were carried out to confirm that the diblock copolymers were formed. In aqueous media this copolymer formed self‐associated polymer micelles that have a carboxyl group on the surface. The carboxyl groups located at the outer shell of the polymeric micelle were expected to combine with ligands to target specific cell populations. The diameter of the polymer micelles was in the range of 30–80 nm. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3527–3536, 2004     

Synthesis of poly(chloromethylstyrene‐b‐styrene) block copolymers by controlled free‐radical polymerization

The controlled free‐radical polymerization of styrene and chloromethylstyrene monomers in the presence of 2,2,6,6‐tetramethyl‐1‐piperidinyloxyl (TEMPO) has been studied with the aim of synthesizing block copolymers with well‐defined structures. First, TEMPO‐capped poly(chloromethylstyrene) was prepared. Among several initiating systems [self‐initiation, dicumyl peroxide, and 2,2′‐azobis(isobutyronitrile)], the last offered the best compromise for obtaining a good control of the polymerization and a fast polymerization rate. The rate of the TEMPO‐mediated polymerization of chloromethylstyrene was independent of the initial concentration of TEMPO but unexpectedly higher than the rate of the thermal self‐initiated polymerization of chloromethylstyrene. Transfer reactions to the chloromethyl groups were thought to play an important role in the polymerization kinetics and the polydispersity index of the resulting poly(chloromethylstyrene). Second, this first block was used as a macroinitiator in the polymerization of styrene to obtain the desired poly(chloromethylstyrene‐b‐styrene) block copolymer. The kinetic modeling of the block copolymerization was in good agreement with experimental data. The block copolymers obtained in this work exhibited a low polydispersity index (weight‐average molecular weight/number‐average molecular weight < 1.5) and could be chemically modified with nucleophilic substitution reactions on the benzylic site, opening the way to a great variety of architectures. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3845–3854, 2000