The preparation of a star triblock copolymer based on polystyrene, poly(ethylene oxide), and poly(methacrylic acid) blocks (S-St-EO-MAA) is described. The polymer structure was achieved by the following route: the polystyrene macroanion (PSm) was formed first by a butyllithium-initiated polymerization of styrene and capping with Michler's ketone; the resulting N,N,N′,N′-tetramethyl-4,4′-diaminodiphenylmethanol (TDDM)-terminated polystyrene was further reacted with metal potassium. The oxo-anion initiated the ring-opening polymerization of ethylene oxide, and the desired ABC triblock copolymer was obtained by precipitation polymerization of methacrylic acid (MAA) initiated with a charge transfer complex (CTC) under UV irradiation using benzene as a solvent. The complex is composed of PS-b-PEO with a TDDM end group (PS-b-PEOtm) and benzophenone (BP). 相似文献
Summary: A novel ABC triblock copolymer with a rigid‐rod block was synthesized by atom transfer radical polymerization (ATRP). First, a poly(ethylene oxide) (PEO)‐Br macroinitiator was synthesized by esterification of PEO with 2‐bromoisobutyryl bromide, which was subsequently used in the preparation of a poly(ethylene oxide)‐block‐poly(methyl methacrylate) (PEO‐b‐PMMA) diblock copolymer by ATRP. A poly(ethylene oxide)‐block‐poly(methyl methacrylate)‐block‐poly{2,5‐bis[(4‐methoxyphenyl)oxycarbonyl]styrene} (PEO‐b‐PMMA‐b‐PMPCS) triblock copolymer was then synthesized by ATRP using PEO‐b‐PMMA as a macroinitiator.
ABC triblock copolymer with a rigid‐rod block. 相似文献
Amphiphilic triblock copolymers of poly(methyl methacrylate)-b-poly(ethylene oxide)-b-poly(methyl methacrylate) (PMMA-b-PEO-b-PMMA) with well-defined structure were synthesized via atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) initiated by the PEO macroinitiator. The macroinitiator and triblock copolymer with different PMMA and/or PEO block lengths were characterized with 1H and 13C NMR and gel permeation chromatography (GPC). The micelle formed by these triblock copolymers in aqueous solutions was detected by fluorescence excitation and emission spectra of pyrene probe. The critical micelle concentration (CMC) ranged from 0.0019 to 0.016 mg/mL and increased with increasing PMMA block length, while the PEO block length had less effect on the CMC. The partition constant Kv for pyrene in the micelle and in aqueous solution was about 105. The triblock copolymer appeared to form the micelles with hydrophobic PMMA core and hydrophilic PEO loop chain corona. The hydrodynamic radius Rh,app of the micelle measured with dynamic light scattering (DLS) ranged from 17.3 to 24.0 nm and increased with increasing PEO block length to form thicker corona. The spherical shape of the micelle of the triblock copolymers was observed with an atomic force microscope (AFM). Increasing hydrophobic PMMA block length effectively promoted the micelle formation in aqueous solutions, but the micelles were stable even only with short PMMA blocks. 相似文献
In the preparation of the ABC star triblock copolymer of ethylene oxide, styrene and methyl methacrylate (MMA), the photo-induced
charge-transfer complex (CTC) was used to initiate the polymerization of the third monomer MMA. The CTC was composed of the
diblock copolymer of poly(ethylene oxide) (PEO) and polystyrene (PS), PEO-bi-PS, with an aromatic imino group at the conjunction point and benzophenone (BP). It was confirmed that the kinetic behavior
of this macromolecular initiation system is nearly the same with a general small radical initiator: the polymerization rate
Rp ∝ [PEO-bi-PS]0.48[BP]0.45[MMA]0.97. Moreover, if the molecular weight of the PEO block is fixed, Rp is independent of the molecular weight of the PS block. By means of measurements of viscosity and fluorescence, it was
found that the micelles of the diblock copolymer PEO-bi-PS were formed in benzene. The aromatic imino groups were located on the boundary surfaces of the micelles and were fully
exposed, and so the BP and MMA molecules easily approached them and affected the charge-transfer polymerization of MMA.
Received: 18 August 1998 Accepted in revised form: 25 November 1998 相似文献
Summary: Based on a hydrophilic poly(ethylene oxide) macroinitiator (PEOBr), a novel amphiphilic diblock copolymer PEO‐block‐poly(11‐(4‐cyanobiphenyloxy)undecyl) methacrylate) (PEO‐b‐PMA(11CB)) was prepared by atom transfer radical polymerization (ATRP) using CuCl/1,1,4,7,10,10‐hexamethyltriethylenetriamine as a catalyst system. An azobenzene block of poly(11‐[4‐(4‐butylphenylazo)phenoxyl]undecyl methacrylate) was then introduced into the copolymer sequence by a second ATRP to synthesize the corresponding triblock copolymer PEO‐b‐PMA(11CB)‐b‐PMA(11Az). Both of the amphiphilic block copolymers had well‐defined structures and narrow molecular‐weight distributions, and exhibited a smectic liquid‐crystalline phase over a wide temperature range.
The amphiphilic triblock copolymer synthesized here. 相似文献
A novel ABA-type triblock copolymer, where A and B correspond to azobenzene (Az) containing polymethacrylate and poly(ethylene oxide) (PEO), respectively, was synthesized by atom transfer radical polymerization. Langmuir-Blodgett monolayers showed characteristic microphase separation structures depending on the isomerization state of the Az unit. The trans-to-cis isomerization induced an anisotropic elongation of the domain of the Az polymer parallel to the rod maintaining the width. Thus, successful photocontrol of nanostructures formed by the block copolymer in the two dimensions was performed. A plausible model for the Az packing and PEO conformation is proposed. 相似文献
Polystyrene–poly(ethylene oxide) PS–PEO di- and triblock copolymers have been used as stabilizers in the emulsion polymerization of styrene and styrene–butylacrylate for the preparation of “hairy latexes”. The polymerization kinetics and the efficiency of these polymeric surfactants were correlated with the molecular characteristics of the block copolymer. It was shown that the efficiency decreased with increasing molecular weight and PS content of the block copolymer. The PEO frige, with a thickness of 4–25 nm, on the latex particle surface could be characterized and it was shown by differential scanning calorimetry (DSC) that water is strucured in that PEO layer. Film formation with “hairy latexes” was also examined both by DSC and thermomechanical analysis. The properties and application possibilities, such as in controlled latex flocculation, have been reviewed. 相似文献
A block copolymer of methyl methacrylate with poly(ethylene oxide) was synthesized by initiation with poly(ethylene oxide) radicals formed by high-speed stirring. The effects of the concentration of the monomer, the concentration of the polymer, the degree of polymerization, the rotation speed, and the solvent on the rate of copolymerization were studied. It was found that the rate of copolymerization was proportional to the concentration of the monomer and to the square root of the rate of scission of the polymer chain. The block copolymerization of methyl methacrylate monomer and styrene monomer (1 : 1 mole ratio) with poly(ethylene oxide) radicals was also carried out by the same method and it was found that the block copolymerization was a radical one. 相似文献
Summary: Spherical micelles have been formed by mixing, in DMF, a poly(styrene)‐block‐poly(2‐vinylpyridine)‐block‐poly(ethylene oxide) (PS‐block‐P2VP‐block‐PEO) triblock copolymer with either poly(acrylic acid) (PAA) or a tapered triblock copolymer consisting of a PAA central block and PEO macromonomer‐based outer blocks. Noncovalent interactions between PAA and P2VP result in the micellar core while the outer corona contains both PS and PEO chains. Segregation of the coronal chains is observed when the tapered copolymer is used.
Inclusion of comb‐like chains with short PEO teeth in the corona triggers the nanophase segregation of PS and PEO as illustrated here (PS = polystyrene; PEO = poly(ethylene oxide)). 相似文献
Hydroxy‐telechelic poly(methyl methacrylate)s of molecular weights below 5000 were obtained by atom transfer radical polymerization (ATRP) of methyl methacrylate followed by end‐capping with allyl alcohol via atom transfer radical addition (ATRA). As initiators for the ATRP, monofunctional initiators with an additional hydroxy group in the molecule or bifunctional initiators were employed. The successful synthesis of the hydroxy‐telechelic PMMA was proved by determination of their molecular weight using MALDI‐TOF‐MS. The efficiency of the end‐capping reaction was determined by 1H NMR spectroscopy using the allyl N‐(4‐tolyl)carbamate as end‐capping agent. Block copolymers comprising a poly(ethylene oxide) (PEO) block and a poly(methyl methacrylate) (PMMA) block were prepared by ATRP using a macroinitiator on the PEO basis. The dormant species of the macroinitiator consists of the phenyl chloroacetate moiety which shows a high rate of initiation. The successful synthesis of the poly(ethylene oxide)‐block‐poly(methyl methacrylate) was proved by 1H NMR spectroscopy; the ratios of EO/MMA repeating units in the feed and the copolymer were nearly equal. 相似文献