Synthesis and characterization of PBMA‐b‐PSt‐b‐PBMA triblock copolymers by atom transfer radical emulsion polymerization

Poly(n‐butyl methacrylate)‐b‐polystyrene‐b‐poly(n‐butyl methacrylate) (PBMA‐b‐PSt‐b‐PBMA) triblock copolymers were successfully synthesized by emulsion atom transfer radical polymerization (ATRP). Difunctional polystyrene (PSt) macroinitiators that contained alkyl chloride end‐groups were prepared by ATRP of styrene (St) with CCl₄ as initiator and were used to initiate the ATRP of butyl methacrylate (BMA). The latter procedure was carried out at 85°C with CuCl/4,4′‐di (5‐nonyl)‐2,2′‐bipyridine (dNbpy) as catalyst and polyoxyethylene (23) lauryl ether (Brij35) as surfactant. Using this technique, triblock copolymers consisting of a PSt center block and PBMA terminal blocks were synthesized. The polymerization was nearly controlled, ATRP of St from those macroinitiators showed linear increases in the number average molecular weight (Mn) with conversion. The block copolymers were characterized with infrared (IR) spectroscopy, hydrogen‐1 nuclear magnetic resonance (¹HNMR), and differential scanning calorimetry (DSC). The effects of the molecular weight of macroinitiators, concentration of macroinitiator, catalyst, emulsion, and temperature on the polymerization were also investigated. Thermodynamic data and activation parameters for the ATRP were also reported. POLYM. ENG. SCI., 45:1508–1514, 2005. © 2005 Society of Plastics Engineers     

Synthesis of block copolymers from PDMS macroinitiators

The synthesis of polystyrene‐b‐polydimethylsiloxane‐b‐polystyrene (PSt‐b‐PDMS‐b‐PSt) copolymers is described. Commercially available difunctional PDMS containing vinylsilyl terminal species was reacted with hydrogen bromide resulting in the PDMS macroinitiators. The terminal alkyl bromide groups were then used as initiators for atom transfer radical polymerization (ATRP) to produce block copolymers. Using this technique, triblock copolymers consisting of a PDMS centre block and polystyrene terminal blocks were synthesized. ATRP of St from those macroinitiators showed linear increases in M_n with conversion, demonstrating the effectiveness of ATRP to synthesize a variety of inorganic/organic polymer hybrids. Copyright © 2004 Society of Chemical Industry     

Synthesis and characterization of PBMA‐b‐PDMS‐b‐PBMA copolymers by atom transfer radical polymerization

Poly(butyl methylacrylate)–b–poly(dimethylsiloxane)–b–poly(butyl methylacrylate) (PBMA–b–PDMS–b–PBMA) triblock copolymers were synthesized by atom transfer radical polymerization (ATRP). The reaction of α,ω‐dichloride PDMS with 2′‐hydroxyethyl‐2‐bromo‐2‐methylpropanoate gave suitable macroinitiators for the ATRP of BMA. The latter procedure was carried out at 110°C in a phenyl ether solution with CuCl and 4,4′‐di (5‐nonyl)‐2,2′‐bipyridine (dNbpy) as the catalyzing system. The polymerization was controllable, with the increase of the monomer conversion, there was a nearly linear increase of molecular weight and a decrease of polydispersity in the process of the polymerization, and the rate of the polymerization was first‐order with respect to monomer conversion. The block copolymers were characterized with IR and ¹H‐NMR and differential scanning calorimetry. The effects of macroinitiator concentration, catalyst concentration, and temperature on the polymerization were also investigated. Thermodynamic data and activation parameters for the ATRP were reported. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 532–538, 2004     

Synthesis and characterization of poly(n‐butyl methacrylate)‐b‐polystyrene diblock copolymers by atom transfer radical emulsion polymerization

Poly(n‐butyl methacrylate) (PBMA)‐b‐polystyrene (PSt) diblock copolymers were synthesized by emulsion atom transfer radical polymerization (ATRP). PBMA macroinitiators that contained alkyl bromide end groups were obtained by the emulsion ATRP of n‐butyl methacrylate with BrCH₃CHCOOC₂H₅ as the initiator; these were used to initiate the ATRP of styrene (St). The latter procedure was carried out at 85°C with CuCl/4,4′‐di(5‐nonyl)‐2,2′‐bipyridine as the catalyst and polyoxyethylene(23) lauryl ether as the surfactant. With this technique, PBMA‐b‐PSt diblock copolymers were synthesized. The polymerization was nearly controlled; the ATRP of St from the macroinitiators showed linear increases in number‐average molecular weight with conversion. The block copolymers were characterized with IR spectroscopy, ¹H‐NMR, and differential scanning calorimetry. The effects of the molecular weight of the macroinitiators, macroinitiator concentration, catalyst concentration, surfactant concentration, and temperature on the polymerization were also investigated. Thermodynamic data and activation parameters for the ATRP are also reported. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 2123–2129, 2005     

Synthesis and characterization of PS‐b‐PDMS‐b‐PS triblock copolymer

A series of polystyrene‐b‐poly(dimethylsiloxane)‐b‐polystyrene (PS/PDMS/PS) triblock copolymers had been synthesized by atom transfer radical polymerization (ATRP). The products had been characterized by Fourier transform infrared, gel permeation chromatography, differential scanning calorimetry, thermogravimetric analysis, contact angle, and scanning electron microscope. The results indicate that the PS chains have been successfully blocked onto the PDMS back bone, and the PS‐b‐PDMS‐b‐PS triblock copolymers have low‐surface tension, good thermal stability, and microphase separation configuration. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Surface microphase separation in PDMS‐b‐PMMA‐b‐PHFBMA triblock copolymer films

Well‐defined poly(dimethylsiloxane)‐block‐poly(methyl methacrylate)‐block‐poly(2,2,3,3,4,4,4‐heptafluorobutyl methacrylate) (PDMS‐b‐PMMA‐b‐PHFBMA) triblock copolymers were synthesized via atom transfer radical polymerization (ATRP). Surface microphase separation in the PDMS‐b‐PMMA‐b‐PHFBMA triblock copolymer films was investigated. The microstructure of the block copolymers was investigated by transmission electron microscopy (TEM) and atomic force microscopy (AFM). Surface composition was studied by X‐ray photoelectron spectroscopy (XPS). The chemical composition at the surface was determined by the surface microphase separation in the PDMS‐b‐PMMA‐b‐PHFBMA triblock copolymer films. The increase of the PHFBMA content could strengthen the microphase separation behavior in the PDMS‐b‐PMMA‐b‐PHFBMA triblock copolymer films and reduce their surface tension. Comparison between the PDMS‐b‐PMMA‐b‐PHFBMA triblock copolymers and the PDMS‐b‐PHFBMA diblock copolymers showed that the introduction of the PMMA segments promote the fluorine segregation onto the surface and decrease the fluorine content in the copolymers with low surface energy. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synthesis of poly(octadecyl acrylate‐b‐styrene‐b‐octadecyl acrylate) triblock copolymer by atom transfer radical polymerization

The synthesis of triblock copolymer poly(octadecyl acrylate‐b‐styrene‐b‐octadecyl acrylate), using atom transfer radical polymerization (ATRP), is reported. The copolymers were prepared in two steps. First, polystyrene was synthesized by ATRP using α,α′‐dichloro‐p‐xylene/CuBr/bpy as the initiating system; Second, polystyrene was further used as macroinitiator for the ATRP of octadecyl acrylate to prepare ABA triblock copolymers in the presence of FeCl₂·4H₂O/PPh₃ in toluene. Polymers with controlled molecular weight (M_n = 17,000–23,400) and low polydispersity index value (1.33–1.44) were obtained. The relationship between molecular weight versus conversion showed a straight line. The effect of reaction temperature on polymerization was also investigated, showing a faster polymerization rate under higher temperature. The copolymers were characterized by FTIR, ¹H‐NMR, DSC, and GPC and the crystallization behavior of the copolymers was also studied. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1539–1545, 2004     

Synthesis and characterization of polystyrene‐b‐poly(ethylene oxide)‐b‐polystyrene triblock copolymers by atom‐transfer radical polymerization

Well‐defined polystyrene (PS)‐b‐poly(ethylene oxide) (PEO)‐b‐PS triblock copolymers were synthesized by atom‐transfer radical polymerization (ATRP), using C—X‐end‐group PEO as macroinitiators. The triblock copolymers were characterized by infrared spectroscopy, nuclear magnetic resonance spectroscopy, and gel permeation chromatography. The experimental results showed that the polymerization was controlled/living. It was found that when the number‐average molecular weight of the macroinititors increased from 2000 to 10,000, the molecular weight distribution of the triblock copolymers decreased roughly from 1.49 to 1.07 and the rate of polymerization became much slower. The possible polymerization mechanism is discussed. According to the Cu content measured with atomic absorption spectrometry, the removal of catalysts, with CHCl₃ as the solvent and kaolin as the in situ absorption agent, was effective. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2882–2888, 2000     

A new macroinitiator for the synthesis of triblock copolymers PA12‐b‐PDMS‐b‐PA12

A new PDMS macroinitiator is proposed for the anionic ring‐opening polymerization of lactams. This α,ω‐dicarbamoyloxy caprolactam PDMS macroinitiator was readily obtained in quantitative yield, by an original synthesis scheme in two steps, which involved the scarcely reported reaction of isocyanates with silanol groups. It was then shown that this bifunctional macroinitiator enabled to synthesize triblock copolymers PA12‐b‐PDMS‐b‐PA12 by polymerization of lauryl lactam (LL) at high temperature (200°C) in inert atmosphere under conditions compatible with reactive extrusion processes. Another related high molar weight α,ω‐diacyllactam PDMS macroinitiator was also successfully used in the polymerization of LL under the same conditions, therefore overcoming the limitations formerly reported for this type of macroinitiators during the polymerization ε‐caprolactam (ε‐CL) at a much lower temperature (80°C). Triblock copolymers with a wide range of PA12 /molar weights (M_n: ～ 10,800–250,000 Da) were eventually obtained by using both types of macroinitiators. DMTA and DSC analyses showed that their thermal properties were strongly dependent upon their respective contents in soft and hard blocks. Such triblock copolymers already appear very promising for the highly effective in situ compatibilization of PA12/PDMS blends as shown by recent complementary results obtained in our laboratory. © 2006 Wiley Periodicals, Inc. J Appl PolymSci 102: 2818–2831, 2006     

Synthesis of defined polyhedral oligosilsesquioxane‐containing diblock and triblock methacrylate copolymers by atom transfer radical polymerization

Defined diblock and triblock copolymers composed of methyl methacrylate‐co‐glycidyl methacrylate block and 3‐{3,5,7,9,11,13,15‐hepta(2‐methylpropyl)‐pentacyclo[9.5.1.1^3,9.1^5,15.1^7,13]‐octasiloxan‐1‐yl}propyl methacrylate block(s), i.e., P(MMA‐co‐GMA)‐b‐PiBuPOSSMA and PiBuPOSSMA‐b‐P(MMA‐co‐GMA)‐b‐PiBuPOSSMA, were synthesized by atom transfer radical polymerization (ATRP). First, monofunctional and bifunctional P(MMA‐co‐GMA) copolymers were synthesized by ATRP. Subsequently, these copolymers were successfully used as macroinitiators for ATRP of POSS‐containing methacrylate monomer. The process showed high initiation efficiency of macroinitiators and led to products with low dispersity. The synthesized block copolymers were characterized by size exclusion chromatography, ¹H‐NMR spectroscopy and their glass transition temperatures were determined by differential scanning calorimetry. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Synthesis of polydimethylsiloxane‐block‐polystyrene‐block‐polydimethylsiloxane via polysiloxane‐based macroinitiator in supercritical CO2

Polydimethylsiloxane‐block‐polystyrene‐block‐polydimethylsiloxane (PDMS‐b‐PS‐b‐PDMS) was synthesized by the radical polymerization of styrene using a polydimethylsiloxane‐based macroazoinitiator (PDMS MAI) in supercritical CO₂. PDMS MAI was synthesized by reacting hydroxy‐terminated PDMS and 4,4′‐azobis(4‐cyanopentanoyl chloride) (ACPC) having a thermodegradable azo‐linkage at room temperature. The polymerization of styrene initiated by PDMS MAI was investigated in a batch system using supercritical CO₂ as the reaction medium. PDMS MAI was found to behave as a polyazoinitiator for radical block copolymerization of styrene, but not as a surfactant. The response surface methodology was used to design the experiments. The parameters used were pressure, temperature, PDMS MAI concentration and reaction time. These parameters were investigated at three levels (?1, 0 and 1). The dependent variable was taken as the polymerization yield of styrene. PDMS MAI and PDMS‐b‐PS‐b‐PDMS copolymers obtained were characterized by proton nuclear magnetic resonance and infrared spectroscopy. The number‐ and weight‐average molecular weights of block copolymers were determined by gel permeation chromatography. Copyright © 2004 Society of Chemical Industry     

Synthesis,characterization, and application of novel amphiphilic poly(D‐gluconamidoethyl methacrylate)‐b‐polyurethane‐b‐ poly(D‐gluconamidoethyl methacrylate) triblock copolymers

Novel amphiphilic ABA‐type poly(D ‐gluconamidoethyl methacrylate)‐b‐polyurethane‐b‐poly(D ‐gluconamidoethyl methacrylate) (PGAMA‐b‐PU‐b‐PGAMA) tri‐block copolymers were successfully synthesized via the combination of the step‐growth and copper‐catalyzed atom transfer radical polymerization (ATRP). Dihydroxy polyurethane (HO‐PU‐OH) was synthesized by the step‐growth polymerization of hexamethylene diisocyanate with poly(tetramethylene glycol). PGAMA‐b‐PU‐b‐PGAMA block copolymers were synthesized via copper‐catalyzed ATRP of GAMA in N, N‐dimethyl formamide at 20°C in the presence of 2, 2′‐bipyridyl using Br‐PU‐Br as macroinitiator and characterized by ¹H‐NMR spectroscopy and GPC. The resulting block copolymer forms spherical micelles in water as observed in TEM study, and also supported by ¹H NMR spectroscopy and light scattering. Miceller size increases with increase in hydrophilic PGAMA chain length as revealed by DLS study. The critical micellar concentration values of the resulting block copolymers increased with the increase of the chain length of the PGAMA block. Thermal properties of these block copolymers were studied by thermo‐gravimetric analysis, and differential scanning calorimetric study. Spherical Ag‐nanoparticles were successfully synthesized using these block copolymers as stabilizer. The dimension of Ag nanoparticle was tailored by altering the chain length of the hydrophilic block of the copolymer. A mechanism has been proposed for the formation of stable and regulated Ag nanoparticle using various chain length of hydrophilic PGAMA block of the tri‐block copolymer. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Atom transfer radical polymerization of styrene and methyl (meth)acrylates initiated with poly(dimethylsiloxane) macroinitiator: Synthesis and characterization of triblock copolymers

Poly(dimethylsiloxane)(PDMS)‐based triblock copolymers were successfully synthesized via atom transfer radical polymerization (ATRP) initiated with bis(bromoalkyl)‐terminated PDMS macroinitiator (Br‐PDMS‐Br). First, Br‐PDMS‐Br was prepared by reaction between the bis(hydroxyalkyl)‐terminated PDMS and 2‐bromo‐2‐methylpropionyl bromide. PSt‐b‐PDMS‐b‐PSt, PMMA‐b‐PDMS‐b‐PMMA and PMA‐b‐PDMS‐b‐PMA triblock copolymers were then synthesized via ATRP of styrene (St), methyl methacrylate (MMA) and methyl acrylate (MA), respectively, in the presence of Br‐PDMS‐Br as a macroinitiator and CuCl/PMDETA as a catalyst system at 80 ^oC. Triblock copolymers were characterized by FTIR, ¹H‐NMR and GPC techniques. GPC results showed linear dependence of the number‐average molecular weight on the conversion as well as the narrow polydispersity indicies (PDI < 1.57) for the synthesized triblock copolymers which was lower than that of Br‐PDMS‐Br macroinitiator (PDI = 1.90), indicating the living/controlled characteristic of the reaction. Also, there was a very good agreement between the number‐average molecular weight calculated from ¹HNMR spectra and that calculated theoretically. Results showed that resulting copolymers have two glass transition temperatures, indicating that triblock copolymers have microphase separated morphology. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Synthesis of poly(fluorinated styrene)‐block‐poly(ethylene oxide) amphiphilic copolymers via atom transfer radical polymerization: potential application as paper coating materials

BACKGROUND: The surface of a substrate which comprises a fibrous material is brought into contact with a type of amphiphilic block copolymer which comprises hydrophilic/hydrophobic polymeric blocks. These amphiphilic copolymers have been synthesized by atom transfer radical polymerization (ATRP) technique. The atom transfer radical polymerization of poly(2,3,4,5,6‐pentafluorostyrene)‐block‐poly(ethylene oxide) (PFS‐b‐PEO) copolymers (di‐ and triblock structures) with various ranges of PEO molecular weights was initiated by a PEO chloro‐telechelic macroinitiator. The polymerization, carried out in bulk and catalysed by copper(I) chloride in the presence of 2,2′‐bipyridine ligand, led to A–B–A amphiphilic triblock and A–B amphiphilic diblock structures. RESULTS: With most of the macroinitiators, the living nature of the polymerizations led to block copolymers with narrow molecular weight distributions (1.09 < M_w/M_n < 1.33) and well‐controlled molecular structures. These block copolymers turned out to be water‐soluble through adjustment of the PEO block content (>90 wt%). Of all the block copolymers synthesized, PFS‐b‐PEO(10k)‐b‐PFS containing 10 wt% PFS was found to retard water absorption considerably. CONCLUSION: The printability of paper treated with the copolymers was evaluated with contact angle measurements and felt pen tests. The adsorption of such copolymers at the solid/liquid interface is relevant to the wetting and spreading of liquids on hydrophobic/hydrophilic surfaces. Copyright © 2009 Society of Chemical Industry     

Synthesis and properties of polystyrene‐b‐poly(ethylene oxide)‐b‐polystyrene triblock copolymers

A series of well‐defined and property‐controlled polystyrene (PS)‐b‐poly(ethylene oxide) (PEO)‐b‐polystyrene (PS) triblock copolymers were synthesized by atom‐transfer radical polymerization, using 2‐bromo‐propionate‐end‐group PEO 2000 as macroinitiatators. The structure of triblock copolymers was confirmed by ¹H‐NMR and GPC. The relationship between some properties and molecular weight of copolymers was studied. It was found that glass‐transition temperature (T_g) of copolymers gradually rose and crystallinity of copolymers regularly dropped when molecular weight of copolymers increased. The copolymers showed to be amphiphilic. Stable emulsions could form in water layer of copolymer–toluene–water system and the emulsifying abilities of copolymers slightly decreased when molecular weight of copolymers increased. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 727–730, 2006     

Synthesis and characterization of novel polystyrene‐block‐polyurethane‐block‐polystyrene tri‐block copolymers through atom transfer radical polymerization

Background: Radical polymerization is used widely to polymerize more than 70% of vinyl monomers in industry, but the control over molecular weight and end group of the resulting polymers is always a challenging task with this method. To prepare polymers with desired molecular weight and end groups, many controlled radical polymerization (CRP) ideas have been proposed over the last decade. Atom transfer radical polymerization (ATRP) is one of the successful CRP techniques. Using ATRP, there is no report on the synthesis of polystyrene‐block‐polyurethane‐block‐polystyrene (PSt‐b‐PU‐b‐PSt) tri‐block copolymers. Hence this paper describes the method of synthesizing these tri‐block copolymers. To accomplish this, first telechelic bromo‐terminated polyurethane was synthesized and used further to synthesize PSt‐b‐PU‐b‐PSt tri‐block copolymers using CuBr as a catalyst and N,N,N,N″,N″‐pentamethyldiethylenetriamine as a complexing agent. Results: The ‘living’ nature of the initiating system was confirmed by linear increase of number‐average molecular weight and conversion with time. A semi‐logarithmic kinetics plot shows that the concentration of propagating radical is steady. The results from nuclear magnetic resonance spectroscopy, gel permeation chromatography and differential scanning calorimetry show that the novel PSt‐b‐PU‐b‐PSt tri‐block copolymers were formed through the ATRP mechanism. Conclusion: For the first time, PSt‐b‐PU‐b‐PSt tri‐block copolymers were synthesized through ATRP. The advantage of this method is that the controlled incorporation of polystyrene block in polyurethane can be achieved by simply changing the polymerization time. Copyright © 2007 Society of Chemical Industry     

The potential of Cu(I)Cl/2,2′‐bipyridine catalysis in a triblock copolymer preparation by atom transfer radical polymerization

The ability of atom transfer radical polymerization (ATRP) in the sequential synthesis of triblock copolymers was examined using Cu(I)Cl/2,2′‐bipyridine catalysis at 110°C in toluene, starting from PMMA macroinitiators terminated with the C‐Br group. The PMMAs were prepared by living anionic or group transfer polymerization (GTP), followed by bromination of the respective active site with Br₂ or N‐bromosuccinimide (NBS). The yield of the terminal bromination in the products of both living polymerizations was 60–64% at best, compared with the yield of the bromination of 1‐methoxy‐(1‐trimethylsilyloxy)prop‐1‐ene (a model of the GTP active site) with NBS, as found by ¹H‐NMR. The PMMA macroinitiators prepared were utilized to start the sequential ATRP, finally affording PMMA‐b‐PBuA‐b‐PSt (M_n 69,100), PMMA‐b‐PSt‐b‐PBuA (M_n 21,300) and PMMA‐b‐PSt‐b‐PMMA (M_n 35,200), which have not yet been synthesized by ATRP. After the second block has been formed, the Br‐unterminated part of PMMA macroinitiator was removed by extraction or repeated precipitation. In the third (last) sequence polymerization, induction periods were observed. The first two triblock copolymers were free of precursors and have M_w/M_n values 1.5–1.6 (SEC). In the course of the last step of PMMA‐b‐PSt‐b‐PMMA synthesis, the content of the PMMA‐b‐PSt precursor slowly decreased with increasing MMA conversion. Still, at ≈90% MMA conversion, about 10–15% of the precursor remained in the product. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 3514–3522, 2001     

Preparation and characterization of polystyrene–poly(ethylene oxide) amphiphilic block copolymers via atom transfer radical polymerization: Potential application as paper coating materials

Poly(ethylene oxide) (PEO) monochloro macroinitiators or PEO telechelic macroinitiators (Cl‐PEO‐Cl) were prepared from monohydroxyfunctional or dihydroxyfunctional PEO and 2‐chloro propionyl chloride. These macroinitiators were applied to the atom transfer radical polymerization of styrene (S). The polymerization was carried out in bulk at 140°C and catalyzed by Copper(I) chloride (CuCl) in the presence of 2,2′‐bipyridine (bipy) ligand (CuCl/bipy). The amphiphilic copolymers were either A‐B diblock or A‐B‐A triblock type, where A block is polystyrene (PS) and B block is PEO. The living nature of the polymerizations leads to block copolymers with narrow molecular weight distribution (1.072 < M_w/M_n < 1.392) for most of the macroinitiators synthesized. The macroinitiator itself and the corresponding block copolymers were characterized by FTIR, ¹H NMR, and SEC analysis. By adjusting the content of the PEO blocks it was possible to prepare water‐soluble/dispersible block copolymers. The obtained block copolymers were used to control paper surface characteristics by surface treatment with small amount of chemicals. The printability of the treated paper was evaluated with polarity factors, liquid absorption measurements, and felt pen tests. The adsorption of such copolymers at the solid/liquid interface is relevant to the wetting and spreading of liquids on hydrophobic/hydrophilic surfaces. From our study, it is observed that the chain length of the hydrophilic block and the amount of hydrophobic block play an important role in modification of the paper surface. Among all of block copolymers synthesized, the PS‐b‐PEO‐b‐PS containing 10 wt % PS was found to retard water absorption considerably. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4304–4313, 2006     

Synthesis of poly[(decanoic acid)‐block‐styrene] diblock copolymers and their self‐assembly behavior in aqueous medium

Diblock copolymers, poly[(10‐hydroxydecanoic acid)‐block‐styrene] (PHDA‐b‐PSt), were synthesized by combining enzymatic condensation polymerization of HDA and atom transfer radical polymerization (ATRP) as of St PHDA was first obtained via enzymatic condensation polymerization catalyzed by Novozyme‐435. Subsequently, one terminus of the PHDA chains was modified by reaction with α‐bromopropionyl bromide and the other terminus was protected by chlorotrimethylsilane. The resulting monofunctional macroinitiator was used subsequently in ATRP of St using CuCl/2,2′‐bipyridine as the catalyst system to afford diblock copolymers including biodegradable PHDA blocks and well‐defined PSt blocks. Polymeric nanospheres were prepared by self‐assembly of the PHDA‐b‐PSt diblock copolymers in aqueous medium. Copyright © 2008 Society of Chemical Industry     

Synthesis of block copolymers with thermodynamically compatible chain segments: di‐ and triblock copolymers of polystyrene and poly(2,6‐dimethyl‐1,4‐phenylene oxide)

Mono‐ and bifunctional poly(phenylene oxide) (PPO) macroinitiators for atom transfer radical polymerization (ATRP) were prepared by esterification of mono‐ and bishydroxy telechelic PPO with 2‐bromoisobutyryl bromide. The macroinitiators were used for ATRP of styrene to give block copolymers with PPO and polystyrene (PS) segments, namely PPO‐block‐PS and PS‐block‐PPO‐block‐PS. Various ligands were studied in combination with CuBr as ATRP catalysts. Kinetic investigations revealed controlled polymerization processes for certain ligands and temperature ranges. Thermal analysis of the block copolymers by means of DSC revealed only one glass transition temperature as a result of the compatibility of the PS and PPO chain segments and the formation of a single phase; this glass transition temperature can be adjusted over a wide temperature range (ca 100–199 °C), depending on the composition of the block copolymer. Copyright © 2005 Society of Chemical Industry