可控自由基聚合技术在涂料树脂合成中的应用

可控自由基聚合技术（CRP）作为一种能够实现对产品分子结构控制的新型聚合方法,对于合成高性能树脂和高分子助剂而言,具有特别重要的意义。本文对主要的可控聚合方法反应机理进行简述,并介绍可控聚合法在高固体分涂料树脂、功能型涂料树脂和水性树脂合成中的应用。     

“活性”自由基聚合的研究现状及发展趋势

以原子转移自由基聚合为重点,结合作者在这一领域的研究成果,简要综述了“活性”（可控）自由基聚合进展。     

原子转移自由基聚合研究进展

原子转移自由基聚合(ATRP)反应是实现活性聚合的一种颇为有效的途径,可以合成分子量可控、分子量分布窄的各种聚合物.介绍了ATRP的研究进展,包括ATRP反应的特点、聚合反应机理、应用、研究现状及前景展望.     

Iron-mediated reversible deactivation controlled radical polymerization

Metal-mediated reversible deactivation radical polymerization (RDRP) is now a cornerstone of functional polymer synthesis, dominated by copper complexes and the Atom Transfer Radical Polymerization (ATRP) moniker. A limitation of this approach is the contamination of the resultant polymers by the coloured copper complexes, thus requiring further purification, although protocols to reduce the amount of copper catalyst have been developed. Iron is an interesting alternative because of its low cost, low toxicity and reduced intensity of its optical absorption spectrum. Use of this metal in RDRP began in the late 90s and has continuously intensified. This review comprehensively covers all the work reported so far on RDRP mediated by iron complexes, organized according to ligand type, and discusses the specificities of this metal in terms of the multitude of accessible spin states and the interplay of different equilibria: atom transfer vs. direct radical trapping, associative vs. dissociative exchange, chain transfer by direct β-H atom transfer vs. β-H elimination from the dormant alkyl species.     

Organometallic mediated radical polymerization

Controlled radical polymerization has become increasingly important over the past decade and a half, allowing for the facile synthesis of specific macromolecular architectures with excellent control over the chemical and physical properties. This article presents an organized and detailed review of one particular CRP technique, organometallic mediated radical polymerization (OMRP), focusing on the individual catalysts developed, their efficacy and monomer scope. Rhodium, cobalt, molybdenum, osmium, iron, palladium, titanium, chromium and vanadium mediated radical polymerizations are presented alongside organo-main group mediated reactions. A separate section reviews the types of copolymers which have been synthesized using OMRP techniques. An attempt is made to unify the many disparate names which have previously been used for OMRP by virtue of the common mechanistic aspects displayed by the different catalyst systems. A mechanistic discussion highlights the similarities and differences between these systems and examines the interplay between reversible termination and degenerative transfer OMRP and competing 1-electron redox processes.     

Facile atom transfer radical homo and block copolymerization of higher alkyl methacrylates at ambient temperature using CuCl/PMDETA/quaternaryammonium halide catalyst system

Controlled polymerization of higher alkyl methacrylates, e.g. lauryl methacrylate (LMA) and stearyl methacrylate (SMA) has been successfully achieved by atom transfer radical polymerization (ATRP) at ambient temperature using CuCl/N,N,N′,N′,N″-pentamethyldiethylenetriamine (PMDETA)/tricaprylylmethylammonium chloride (Aliquat^®336) as the catalyst system and ethyl 2-bromoisobutyrate or 2,2,2-trichloroethanol as the initiator. Although the bulk polymerization gives satisfactory control, the latter becomes better when anisole or THF is added into the system. Without AQCl the control was lost. A large deviation of molecular weight from theory has been observed which has been attributed to the very high-molecular weight of the dead polymers formed during the building-up of the persistent radical. The controlled polymers have been used as macroinitiators for block (di, tri and penta) ATR copolymerization with several methacrylates.     

Heterografted PEO-PnBA brush copolymers

A series of P[(HEMA-TMS)-co-PEOMA] graft copolymers with different amounts of incorporated macromonomer grafts were prepared by copolymerization of a PEO macromonomer (PEOMA, MW_av=1100 g/mol, DP_PEO=23) with 2-(trimethylsilyloxy)ethyl methacrylate (HEMA-TMS) using various initial ratios of the comonomers via atom transfer radical polymerization. After transformation of the HEMA-TMS units to 2-(2-bromopropionyloxy)ethyl methacrylate (BPEM), the resulting P(BPEM-co-PEOMA) copolymers were used as macroinitiators for the controlled polymerization of nBA in a ‘grafting from’ reaction. The resulting densely heterografted brush copolymers with a uniform length of PEO grafts (DP_PEO=23) and a range of lengths for the PnBA side chains (DP_PnBA=15-60) depending solely on the reaction time. Analysis of the bulk properties showed that the specific architecture of the copolymers suppresses crystallization of the PEO, and consequently leads to amorphous, homogeneous materials.     

High-pressure atom transfer radical polymerization of methyl methacrylate for well-defined ultrahigh molecular-weight polymers

The feasibility of high-pressure atom transfer radical polymerization (ATRP) for synthesizing well-defined polymers of extraordinarily high molecular weights was demonstrated. ATRP of methyl methacrylate (MMA) under pressures up to 500 MPa was investigated at 60 °C. The addition of a small amount of a Cu(II)Cl₂/ligand complex along with the general benefits of high pressure of enhancing propagation and suppressing termination brought about an excellent control of polymerization even with an extremely low concentration of ATRP initiator. For example, there was produced PMMA with a number-average molecular weight M_n of 3.6 × 10⁶ and a polydispersity index of 1.24, which had never been achieved by conventional ATRP.     

活性自由基乳液聚合的研究进展

活性自由基乳液聚合是一个非常新的研究领域。介绍了目前活性自由基乳液聚合领域的3种常用的方法及应用这些方法进行乳液聚合的研究进展,包括:原子转移自由基聚合(ATRP),氮氧调节自由基聚合(NMP)和可逆加成-断裂链转移自由基聚合(RAFT)。     

Effects of molecular weight on liquid-crystalline behavior of a mesogen-jacketed liquid crystal polymer synthesized by atom transfer radical polymerization

The synthesis of poly{2,5-bis[(4-methoxyphenyl)oxycarbonyl]styrene} (PMPCS) with different molecular weight and low polydispersity was achieved by atom transfer radical polymerization in methoxybenzene solution using 1-bromoethylbenzene as an initiator and CuBr/sparteine complex as a catalyst. The concentration of the living centers throughout the polymerization was found to be constant. The liquid-crystalline behavior of the polymers with M_n ranging from 3800 to 17,400 g/mol was studied using DSC and POM. Only the polymers with M_n beyond 10,200 g/mol formed a liquid-crystalline phase, which was quite stable with a high clearing point (higher than the decomposition temperature of the polymer).