Diblock and triblock copolymers of styrene and acetoxymethylstyrene by one-pot ATRP (original) (raw)
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Macromolecules, 2002
Atom transfer radical polymerization (ATRP) was successfully applied to the synthesis of styrene-acrylonitrile (SAN) copolymers of predetermined molecular weights and low polydispersities. The monomers were copolymerized under azeotropic conditions (ca. 63 mol % styrene and 37 mol % acrylonitrile) in bulk using mono-and difunctional alkyl halide initiators such as 2-bromopropionitrile, 1-phenylethyl bromide, methyl 2-bromopropionate, poly(ethylene oxide) monomethyl ether 2-bromopropionate, and the bis(2-bromopropionate) esters derived from poly(ethylene oxide), poly(propylene oxide), or poly(-caprolactone) diols of various molecular weights in combination with two catalytic systems: CuBr/2,2′-bipyridine (bpy) and CuBr/N,N,N′,N′′,N′′-pentamethyldiethylenetriamine (PMDETA). The synthesized copolymers had high chain end-functionalities, as proven by further chain extension with styrene, n-butyl, tert-butyl, or glycidyl acrylate, and methyl methacrylate. In the last case, the reaction in the presence of CuBr/bpy led to a block copolymer of high polydispersity, which was decreased to M w/Mn) 1.5 using halogen exchange (i.e., CuCl/bpy as the catalytic system). All other block copolymers (including di-, tri-, and pentablock copolymers) had narrow molecular weight distributions (Mw/Mn) 1.1-1.4).
Journal of Polymer Science Part A: Polymer Chemistry, 2002
Azo-containing polytetrahydrofuran (PTHF) obtained by cationic polymerization was used as a macroinitiator in the reverse atom transfer radical polymerization (RATRP) of styrene and methyl acrylate in conjunction with CuCl 2 / 2,2Ј-bipyridine as a catalyst. Diblock PTHF-polystyrene and PTHF-poly(methyl acrylate) were obtained after a two-step process. In the first step of the reaction, stable chlorine-end-capped PTHF was formed with the thermolysis of azo-linked PTHF at 65-70°C in the presence of the catalyst. Heating the system at temperatures of 100-110°C started the polymerization of the second monomer, which resulted in the formation of block copolymers. The decomposition behavior of the azo-linked PTHF and the structure of the block copolymers were determined by 1 H NMR and gel permeation chromatography (GPC). Kinetic studies and GPC analyses further confirmed the controlled/living nature of the RATRP initiated by the polymeric radicals.
Simple laboratory synthesis of poly (styrene)-block-poly (ethylene glycol)block-poly(styrene) (PS-PEG-PS) tri-block copolymer (TBC) using versatile atom transfer radical polymerization (ATRP) technique is reported. Chloroand Bromo-PEG macroinitiators were synthesized by the transformation of the end group of PEG through 2-chloro or bromo propionyl chloride which was subsequently used in the preparation of symmetrical TBC of PS-PEG-PS under ATRP conditions using styrene as monomers. The PEGmacroinitiators and synthesized TBC were characterized by FT-IR and 1 H-NMR spectroscopy. The average molecular weight and molecular weight distributions of the TBC were obtained using GPC analysis. The experimental results showed that the polymerization was controlled/living with the PDI=1.4. The thermal behaviour and compositional properties of the TBC were studied using TGA.
Polymer Journal, 2005
The transformations of free radical promoted cationic polymerization to atom transfer radical polymerization (ATRP) to form the block copolymers of cyclohexene oxide (CHO) with styrene (St) were performed. In the first step, bromine terminated poly(CHO)s (PCHO-Br) were prepared by free radical promoted cationic polymerization of CHO monomer in the presence of 2-oxo-1,2-diphenylethyl-2-bromopropanoate, shortly bromo benzoin, (B-Br) and an onium salt namely 1-ethoxy-2-methylpyridinium hexafluorophosphate (EMP þ SbF 6 À) as the initiating system. The bromine functionalized polymers thus prepared were used as initiators in ATRP of St, in bulk, in conjunction with CuBr/2,2 0-bipyridine as catalyst gave well-defined block copolymer of CHO and St. Block copolymer formations were evidenced by 1 H NMR and gel permeation chromatography (GPC) measurements. [
Diblock and triblock functional copolymers by controlled radical polymerization
Journal of Polymer Science Part A: Polymer Chemistry, 1999
Controlled polystyrenes with different molar mass values were synthesized starting from benzoyl peroxide and TEMPO (2,2,6,6-tetramethylpiperidinyl-1-oxy). The polystyrene homopolymers served as initiators for the block copolymerization of phthalimide methylstyrene (PIMS) to synthesize polystyrene-b-poly(PIMS) diblock copolymers. Diblock copolymers with well defined structures as well as controlled and narrow molar mass distribution were obtained from the lower-mass polystyrene homopolymers. The lower-mass copolymers were found to be active as initiators in the synthesis of the polystyrene-b-poly(PIMS)-b-polystyrene triblock copolymers. In each reaction step, the effects of conversion and reaction time on the molar mass characteristics of the prepared block copolymers were investigated. The diblock and triblock copolymers were modified using hydrazine as the reagent in order to obtain the corresponding functional amino block copolymers.
European Polymer Journal, 2021
In this study, we report concurrent ring-opening and atom transfer radical polymerization for synthesis of the block copolymers of L-lactide and styrene. Simultaneous polymerization of two different polymerization mechanisms requires careful selection of reaction conditions and reagents for targeted comparable propagation of both types. Several different di-block copolymers are synthesized having different total molar mass, chemical composition, and individual block lengths. Such simultaneous polymerization mechanisms require different reagents, and the regents required for one type of polymerization may hamper the other parallel mechanism. Hence, synthesized block copolymers are analysed comprehensively using different polymer chromatographic techniques and NMR spectroscopy. Total molar mass and chemical composition of BCPs are determined by size exclusion chromatography and NMR, respectively. PLA block length in PS-b-PLA and quantification of PS homopolymers is revealed by liquid chromatography at critical conditions of PS. For determination of PS block length in PS-b-PLA and quantification of PLA homopolymers, a gradient polymer elution chromatography (GPEC) method is applied. The comprehensive analysis of synthesized PS-b-PLA by parallel polymerization mechanisms revealed uninterrupted simultaneous polymerization of both monomers under applied conditions.
Journal of Polymer Science Part A: Polymer Chemistry, 2000
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 2,2Ј-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(chloromethylstyreneb-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 Ͻ 1.5) and could be chemically modified with nucleophilic substitution reactions on the benzylic site, opening the way to a great variety of architectures.
Macromolecular Rapid Communications, 1999
Poly(oxyethylene)s terminated at both ends with 2-bromopropionate end-groups were prepared and characterized by means of MALDI TOF mass spectrometry. It was shown, that atom transfer radical polymerization (ATRP) of methyl methacrylate with a poly(oxyethylene) macroinitiator in bulk proceeds with low initiation efficiency while polymerization of tert-butyl acrylate proceeds with practically quantitative initiation, leading to ABA block copolymers. Originally formed tert-butyl acrylate blocks contain terminal bromine, as expected for the ATRP mechanism. MALDI TOF analysis indicates, however, that in the later stages of polymerization side reactions lead to elimination of terminal bromine.