含端基氯低聚物引发剂的合成及其引发苯乙烯聚合的研究

通过对４种端羟基低聚物进行氯乙酰化反应,制备了一系列含端基氯的低聚物,然后以这些含端基氯的低聚物为大分子引发剂,在ＣｕＣｌ／ｂｐｙ存在下引发苯乙烯的ＡＴＲＰ反应,得到ＡＢＡ嵌段共聚物。用＾１Ｈ－ＮＭＲ分析证明了聚合物的嵌段结构,以ＳＥＣ测定了聚合物的相对分子质量及其分布,发现嵌段聚合物的相对分子质量和单体转化率成正比,并和相对分子质量的理论值Ｍ↑－ｎ,ｔｈ＝（Δ［Ｍ］／［ｏｌｉｇｏｍｅｒ－Ｃｌ］）     

Synthesis of graft copolymers from a linear polyolefin through a combination of coordination polymerization and atom transfer radical polymerization

This article reports on a facile route for the preparation of methyl acrylate and methyl methacrylate graft copolymers via a combination of catalytic olefin copolymerization and atom transfer radical polymerization (ATRP). The chemistry first involved a transforming process from ethylene/allylbenzene copolymers to a polyolefin multifunctional macroinitiator with pendant sulfonyl chloride groups. The key to the success of the graft copolymerization was ascribed to a fast exchange rate between the dormant species and active radical species by optimization of the various experimental parameters. Polyolefin‐g‐poly(methyl methacrylate) and polyolefin‐g‐poly(methyl acrylate) graft copolymers with controlled architecture and various graft lengths were, thus, successfully prepared under dilute ATRP conditions. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

原子转移自由基聚合在合成接枝共聚物中的应用

本文综述了采用原子转移自由基聚合（ATRP）法合成接枝共聚物的研究进展。主要从大分子引发剂法和大分子单体法两方面介绍了原子转移自由基聚合在合成接枝聚合物中的应用。     

Controlled free radical polymerization of styrene initiated by a [BPO-polystyrene-(4-acetamido-TEMPO)] macroinitiator

The bulk polymerization of styrene at 125°C was studied using a [BPO-polystyrene-(4-acetamido-TEMPO)] macroinitiator synthesized by a styrene polymerization in the presence of 4-acetamido-2,2,6,6-tetramethylpiperidine-N-oxyl (4-acetamido-TEMPO) and benzoyl peroxide (BPO). The rates of polymerization were independent of the initial macroinitiator concentration and they were very similar to that for the thermal autopolymerization of styrene. Additionally, different types of N-oxyls did not have any effect on the polymerization rate. The number-average molecular weights (M_n) of the obtained polymers agreed very well with theoretical predictions, deviations were observed only at low macroinitiator concentrations. Increasing macroinitiator concentrations resulted in lower magnitudes of the growing molecular weights and reduced polydispersities (M_w/M_n) at the initial stage of the polymerization. The concentration of the polymer chains was calculated, and it was recognized that the concentration of polymer chains increased during the polymerization as a result of an additional radical formation due to the thermal self-initiation of styrene. This thermal self-initiation could be proved qualitatively by the addition of N-oxyl to a macroinitiator polymerization system.     

Synthesis of polysulfone-b-polystyrene block copolymers by mechanistic transformation from condensation polymerization to free radical polymerization

Synthesis of polysulfone-b-polystyrene (PSU-b-PS) block copolymers by a combination of condensation polymerization and free radical polymerization processes are described. First, a new macroazoinitiator (MAI) containing polysulfone (PSU) units was prepared by direct esterification of 4,4-azobis(4-cyanopentanoic acid) with α,ω-hydroxyl PSU telechelics at ambient conditions. The macroinitiator was then used in conventional free radical polymerization of styrene leading to the formation of desired block copolymers. In this process, initiating macroradicals were generated by thermal cleavage of the azo group present in the macroazoinitiator structure. The precursor polysulfone macroazoinitiator (PSU-MAI) and resulting block copolymers were characterized by spectral analysis using FT-IR, ¹H-NMR, GPC, TGA, and DSC.     

Synthesis of densely grafted copolymers by nitroxide-mediated radical polymerization of styrene using poly(phenylacetylene)s as a macroinitiator

Poly(phenylacetylene)s carrying alkoxyamine moieties in the side chain were prepared by Rh-catalyzed homopolymerization of 1-(4-ethynylphenyl)-1-(2,2,6,6-tetramethyl-1-piperidinyloxyl)ethane (1) and random copolymerization of 1 and 4-methoxy-1-ethynylbenzene (2a) or 4-decyloxy-1-ethynylbenzene (2b). ¹H NMR spectra showed that the poly(phenylacetylene)s adopted a cis-transoid structure. Using the poly(phenylacetylene)s as the macroinitiator the nitroxide-mediated radical polymerization of styrene (St) was carried out at 120 °C to yield densely grafted copolymers as a light yellow powder. The side chain lengths of the graft copolymers were determined by both ¹H NMR and conversion of St, which agreed with each other. The SEC profiles of the graft copolymers were unimodal at low conversions but were not unimodal at high conversion: a shoulder was observed in the high molecular=weight region and a small peak was observed in the low molecular=weight region. ¹H NMR measurements of the graft copolymers indicated that the copolymers adopted a trans-transoid structure, revealing that isomerization from cis-transoid to trans-transoid forms took place during the polymerization of St at 120 °C.     

Synthesis of poly(styrene-co-isopropenyl acetate) -g-polyisobutylene graft copolymers via combination of radical polymerization with cationic polymerization

Random copolymers of poly(styrene-co-isopropenyl acetate) (SIPA) with an average number of 9 initiating sites per chain were synthesized by free radical copolymerization of styrene with a small amount of isopropenyl acetate using 2,2′-azo-bis-(isobutyronitrile) as an initiator at 70 °C. SIPA copolymer could be further used as macroinitiator for the grafting cationic polymerization of isobutylene (IB) from SIPA chain in CH₂Cl₂ at ?40 °C to produce graft copolymers of SIPA-g-PIB. The effect of SIPA concentration ([SIPA]), TiCl₄ concentration ([TiCl₄]) and IB concentration ([IB]) on initiation efficiency of macroinitiator, grafting efficiency of initiating sites, average length of PIB branches of the resulting graft copolymers were investigated. It can be found that almost all of the initiating sites of IPAc units on SIPA chains were active for the cationic polymerization of IB and both initiation efficiency and grafting efficiency were close to 100% at sufficient molar ratio of TiCl₄/IPAc. This synthetic route presents quantitative grafting efficiency and possibility to control length of PIB branches. The graft copolymers of SIPA-g-PIB with average 9-branched PIB chains having terminal functional tert-chlorine groups could be successfully obtained. The average molecular weight of PIB branches in SIPA-g-PIB graft copolymers could be mediated from 3900 to 47,300 g mol^?1 by changing the ratios of macroinitiator to monomer and concentration of TiCl₄.     

Architecture of rod–brush block copolymers synthesized by a combination of coordination polymerization and atom transfer radical polymerization

A combination of coordination polymerization and atom transfer radical polymerization (ATRP) was applied to a novel synthesis of rod–brush block copolymers. The procedure included the following steps: (1) the monoesterification reaction of ethylene glycol with 2-bromoisobutyryl bromide (BIBB) yielded the bifunctional initiator monobromobutyryloxy ethylene glycol and (2) a trichlorocyclopentadienyl titanium (CpTiCl₃; bifunctional initiator) catalyst was prepared from a mixture of CpTiCl₃ and bifunctional initiator. The coordination polymerization of n-butyl isocyanate initiated by such a catalyst provided a well-defined macroinitiator, poly(n-butyl isocyanate)–bromine (PBIC–Br). (3) The ATRP method of 2-hydroxyethyl methacrylate initiated by PBIC–Br provided rod [poly(n-butyl isocyanate) (PBIC)]–coil [poly(2-hydroxyethyl methacrylate) (PHEMA)] block copolymers with a CuCl/CuCl₂/2,2′-bipyridyl catalyst. (4) The esterfication of PBIC-block-PHEMA with BIBB yielded a block-type macroinitiator, and (5) ATRP of methyl methacrylate with a block-type macroinitiator provided rod–brush block copolymers. We found from the solution properties that such rod–brush block copolymers formed nanostructured macromolecules in solution. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Synthesis of PPP-b-PS block copolymers using a combination of Suzuki-polycondensation and nitroxide-mediated radical polymerization

The synthesis of π-conjugated Nitroxide-Mediated Radical Polymerization (NMRP)-macroinitiators by Suzuki-polycondensation in a one-step reaction has been investigated using conventional and microwave-heating in presence of a suitable terminating agent. Alkoxyamine-functionalized poly(para-phenylene)s were initially synthesized by Suzuki-polycondensation and then its block copolymer with styrene by NMRP. Molecular weight and molecular weight distribution of the polymers have been determined in SEC-measurements, while end-group determination was performed with MALDI-ToF-MS. Thin-layer-morphologies of the block copolymers were investigated using tapping-mode AFM.     

Controlled synthesis of vinyl-functionalized homopolymers and block copolymers by RAFT polymerization of vinyl methacrylate

Reversible addition-fragmentation chain transfer (RAFT) polymerization of an asymmetrical divinyl monomer, vinyl methacrylate (VMA), was investigated under various conditions. RAFT polymerization of VMA using a dithioester-type chain transfer agent (CTA) under suitable conditions afforded soluble polymers with a high content of pendant vinyl ester side chains in sufficient yields (>70%). The monomer concentration, the nature of the CTA, and the CTA/initiator ratio were found to affect the polymerization reaction and the structure of the resulting polymers; this behavior is attributed to the relative propensities for intermolecular propagating/cross-linking reactions and intramolecular cyclization. A kinetic study of the RAFT polymerization of VMA with the dithioester-type CTA 1 suggested that the propagation reaction of the methacryloyl group proceeded predominantly with a certain level of intramolecular cyclization during the early stage of the polymerization and intermolecular cross-linking during the final stage of the polymerization. Block copolymers with one segment featuring pendant vinyl functionality were synthesized by RAFT polymerization of VMA using poly(methyl methacrylate) as a macro-chain transfer agent (macro-CTA).     

Blending of polystyrene with styrene-siloxane block and graft copolymers

A preliminary study on the efficiency of styrene-siloxane block and graft copolymer as toughening additives for polystyrene has been made. Block and graft copolymers of required molecular weight were synthesized for making compatible blends with polystyrene. Compatibility of these systems was evaluated through differential scanning calorimetry, thermo-mechanical analysis, rheovibron studies, and scanning electron microscopy. A good miscibility of block and graft copolymers was confirmed by these methods. Higher work of rupture in these blended polystyrene samples further demonstrates the feasibility of styrene-siloxane block and graft copolymers as good toughening material for a brittle polystyrene matrix. The mechanical properties have been related to the morphology and the amount of siloxane content in the blended polystyrene.     

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 and characterization of pH/temperature-sensitive block copolymers via atom transfer radical polymerization

In order to prepare well-defined pH-sensitive block copolymers with a narrow molecular weight distribution (MWD), we synthesized a pH-sensitive block copolymer via atom transfer radical polymerization (ATRP) of sulfamethazine methacrylate monomer (SM) and amphiphilic diblock copolymers by the ring-opening polymerization of d,l-lactide/?-caprolactone (LA/CL), and their sol-gel phase transition was investigated. SM, which is a derivative of sulfonamide, was used as a pH responsive moiety, while PCLA-PEG-PCLA was used as a biodegradable, as well as a temperature sensitive one, amphiphilic triblock copolymer. The pentablock copolymer, OSM-PCLA-PEG-PCLA-OSM, was synthesized using Br-PCLA-PEG-PCLA-Br as an ATRP macroinitiator. The number average molecular weights of SM were controlled by adjusting the monomer/initiator feed ratio. The macroinitiator was synthesized by the coupling of 2-bromoisobutyryl bromide with PCLA-PEG-PCLA in the presence of triethyl amine catalyst in dichloromethane. The resultant block copolymer shows a narrow polydispersity. The block copolymer solution shows a sol-gel transition in response to a slight pH change in the range of 7.2-8.0. Gel permeation chromatography (GPC) and NMR were used for the characterization of the polymers that were synthesized.     

Efficient synthesis of two or multi component block copolymers through living radical polymerization with polymeric photoiniferters

Summary To synthesize efficiently block copolymers, the radical polymerization of vinyl monomers with the polymers obtained by tetraethyl thiuram disulfide(TD) as polymeric photoiniferters has been investigated. These photopolymerizations were found to proceed via a living radical mechanism, i.e. both the whole polymer yields and the average molecular weight of the block copolymers increased with increasing of the polymerization time. By applying these living radical polymerizations, various block copolymers consisting of two, three and four component blocks were obtained in good yields, suggesting that these techniques are effective and useful for synthesizing multi component block copolymers through radical polymerizations of polar vinyl monomers.     

Atom transfer radical polymerization of methyl methacrylate initiated with a macroinitiator of poly(vinyl acetate)

Well‐defined poly(vinyl acetate‐b‐methyl methacrylate) block copolymers were successfully synthesized by the atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) in p‐xylene with CuBr as a catalyst, 2,2′‐bipyridine as a ligand, and trichloromethyl‐end‐grouped poly(vinyl acetate) (PVAc–CCl₃) as a macroinitiator that was prepared via the telomerization of vinyl acetate with chloroform as a telogen. The block copolymers were characterized with gel permeation chromatography, Fourier transform infrared, and ¹H‐NMR. The effects of the solvent and temperature on ATRP of MMA were studied. The control over a large range of molecular weights was investigated with a high [MMA]/[PVAc–CCl₃] ratio for potential industry applications. In addition, the mechanism of the polymerization was discussed. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1089–1094, 2006     

Synthesis of thermoresponsive block and graft copolymers via the combination of living cationic polymerization and RAFT polymerization using a vinyl ether-type RAFT agent

A novel vinyl ether-type RAFT agent, benzyl 2-(vinyloxy)ethyl carbonotrithioate (BVCT) was synthesized for various block copolymers via the combination of living cationic polymerization of vinyl ethers and reversible addition−fragmentation chain transfer (RAFT) polymerization. The novel BVCT–trifluoroacetic acid adduct play an important role to produce well-defined block copolymers, which is both as a cationogen under EtAlCl₂ initiation system in the presence of ethyl acetate for living cationic polymerization and a RAFT agent for blocks by RAFT polymerization. The resulting polymer, poly(vinyl ether)s, by living cationic polymerization had a high number average α-end functionality (≥0.9) as determined by both ¹H NMR and MALDI-TOF-MS spectrometry. In addition, this poly(vinyl ether)s worked well as a macromolecular chain transfer agent for RAFT polymerization. The RAFT polymerization of radically polymerizable monomers was conducted in toluene using 2,2′-azobis(isobutyronitrile) at 70 °C. For example, a double thermoresponsive block copolymer (MOVE₆₁-b-NIPAM₁₅₀) consisting of 2-methoxyethyl vinyl ether (MOVE) and N-isopropylacrylamide (NIPAM) was prepared via the combination of living cationic polymerization and RAFT polymerization. The block copolymer reversibly formed and deformed micellar assemblies above the phase separation temperature (T_ps) of poly(NIPAM) block in water. This BVCT is not only functioned as an initiator, but also acted as a monomer. When BVCT was copolymerized with MOVE by living cationic polymerization, followed by graft copolymerization with NIPAM via RAFT polymerization, well-defined graft copolymers (MOVE_n-co-BVCT_m)-g-NIPAM_x (n = 62–73, m = 1–9, x = 19–214) were successfully obtained. However, no micelle formed in water above T_ps of poly(NIPAM) graft chain unlike the case of block copolymers.     

Stabilization of emulsion polymerization by block and graft copolymers with polysiloxane and poly[(acetylimino)ethylene] sequences

Amphiphilic block and graft copolymers with polysiloxane and poly[(acetylimino)ethylene] sequences were used as nonionic surfactants in the emulsion polymerization of some vinyl monomers (styrene, methyl methacrylate, butyl methacrylate). The peculiarities of the systems (polymerization kinetics and emulsion characteristics) were related to the structural features of the studied emulsifiers and suggested their ability to participate in initiation and transfer reactions and respectively clouding phenomena in aqueous phase.     

New method for controlled synthesis of polylactide block copolymers: organoborane/p-quinone system and reversible-deactivation radical polymerization

We developed a new approach to obtain polylactide hybrid block copolymers with vinyl monomers (styrene, methyl methacrylate, methyl acrylate) through the realization of a reaction sequence using triethylborane and various p-quinones. The method offered includes two stages. In the first stage, a chain-transfer agent was obtained by borylation of the terminal hydroxyl groups of polylactide. The second stage was vinyl monomer radical polymerization in the presence of p-quinone accompanied by S_H2-substitution at the boron atom.1,4-Naphthoquinone, 2,3-dimethyl-1,4-benzoquinone, duroquinone and 2,5-di-tert-butyl-1,4-benzoquinone were used as synthetic polymer chain growth mediators. It is shown that 1,4-naphthoquinone and 2,3-dimethyl-1,4-benzoquinone, similar in their characteristics, are effective agents providing the realization of reversible-deactivation radical polymerization. Realization of reversible-deactivation radical polymerization was proved with the analysis of the kinetics of block copolymerization, molecular weight characteristics and compositional homogeneity of block copolymers as well as its further capability to elongate the polymer chain. Synthesized block copolymers have a high thermal stability compared to the initial borylated polylactide. © 2021 Society of Industrial Chemistry.