Mechanochemically Synthesized Polymers with Special Properties

Abstract

The application of mechanical energy on micro-and macromolecular solid bodies has as a result the formation of some new and energy-rich surfaces, strongly activated and able to develop reactions that are difficult to accomplish in other conditions. By vibratory milling of vinyl monomers in the presence of crystalline inorganic substances, grafted polymers are obtained which can be successfully used as filling materials in poly(viny1 chloride) processing. As a result of mechanical activation, the heterochain macromolecular compounds form new functional groups that are able to react with the judiciously selected micromolecular compounds by polycondensation reactions. This type of synthesis has also been extended to the carbochain polymers. By mechanodegradation, the latter ones form radicallic macromolecular fragments which can be stabilized with acceptors of the aromatic diamine type, leading to the obtainment of new polymers with special mechanical properties. The mechanochemical complexation was activated by vibratory milling, ultrasonic treatment, and cryolisis; the polyamides, cellulose, and polyesters were employed as macromolecular ligands; and the ions of Ti, V, Fe, Ni, and Mn were used as complexing centers. The vibratory milling of vinylic, acrylic, and dienic monomers, of the aromatic rings as well as of the nitriles, can activate their polymerization. The reaction takes place in the absence of any initiator, by a radical or ionic mechanism, as a function of the monomer chemical nature, the medium, and the gaseous atmosphere, respectively. The mechanochemically synthesized products are characterized by high thermostability , special 1025

The mechanochemical synthesis of polymers

“…125,138 Continuing studies by Oprea in the 1980s and by Kuzuya in the 1990s covered many of the vinyl monomers known to undergo polymerisation (Scheme 1). 18 The adopted strategy was used to convert (meth)acrylates, 19,130,[139][140][141][142][143][144][145] (meth)acrylamides, 125,126,141,146 styrenes, 128,141,[147][148][149][150] and other structurally diverse vinyl monomers [149][150][151][152] into the corresponding polymers under solvent-free ball-milling conditions. Moreover, the copolymerisation of these monomers has also been investigated, 125,130,140,149,[153][154][155] as is discussed below.…”

“…Both Oprea and Kuzuya proposed that the initiation step involves electron transfer from the milling material to the substrate. 18,19,126,141 Strong collisions between ball and vessel supply energy greater than the milling materials' work function, i.e. the threshold energy for electron emission.…”

“…The first mechanochemical polymerisation was demonstrated in 1959 by the Kargin group, who used vibrational ball milling to polymerise vinyl monomers. 17 Several sporadic studies followed, including those of vinyl monomer polymerisation by Oprea in the 1980s 18 and by Kuzuya in the 1990s. 19 As mechanochemistry was not well established at that time, these studies did not receive deserved attention.…”

Effect of ultrasonic oscillations on the rheological behavior and morphology of Illite‐filled high‐density polyethylene composites

“…The mechanical properties and processability of polymers will be significantly sacrificed because of the poor dispersion of fillers and weak interactions between fillers and polymer matrices. To achieve homogeneous dispersions of fillers in polymer matrices and to enhance the interactions between fillers and polymer matrices, several methods are generally applied: (1) the surface treatment of fillers with a coupling agent;2, 8, 9 (2) the polar group functionalization of polymers with partial oxidation, γ‐rays, electron beams, microwaves, UV irradiation, or polar grafting;10, 11 (3) the addition of a bifunctional component that can interact with both fillers and matrices;12 and (4) the mechanochemical modification of fillers 13–15…”

Mechanochemically mediated controlled radical polymerization

“…1892 年，Matthew Carey Lea [13] 基于卤化银受力分解的现象，认为机械力是 一种与热、光、电并列的能量形式，但缺乏足够的理论基础。直到 1907 年， Ostward [14] 提 出 力 化 学 的 学 术 概 念 ，他在著作《Handbuch der allgemeinen Chemie》中详细讨论了机械能与化学能的关系，提出了关于力化学的最早假设， 即物质内部原子、分子的位移导致了内摩擦和弹性变形的现象。从那时起，化 学家开始尝试从力化学的角度解释化学反应现象，促进了力化学研究的发展， 通过研磨或球磨的方式也实现了一些有机小分子的合成(图 1(a)) 。Staudinger [17] 在 1930 年将高分子密炼导致的分子量降低现象归因于为大分子的力化学降解。 Kauzmann 和 Eyring [18] 完善了这一观点，提出了机械力导致聚合物主链共价键 均裂的假设(图 1(b)) 。这些开创性的工作带动了聚合物领域对力化学的广泛关 注。四川大学徐僖院士将力化学降解与塑料加工结合，提出并发展了以超声为 主的力化学加工技术，广泛应用于高分子及其复合材料的改性 [19] 、成型 [15,20] 等 领域。如图 1(c)所示，徐僖团队 [15] 磨，开发了磨盘式的固相力 化学反应器，实现了高分子材料常温超细粉碎 [16,21~24] (图 1(d)) 、聚烯烃固相力化学接枝 [25,26] 、固相剪切混合控制聚合物共混 物相结构 [27,28] 和固相剪切制备聚合物/无机复合材料 聚醚醚酮扫描电子显微镜(SEM)照片 [16] Figure 1 Early developments in mechanochemistry. (a) Milling for the preparation of solid conductive polymers [12] ; (b) force-induced macromolecular chain fragment [10] ; (c) ultrasonic synthesis of polyaniline/nano-TiO 2 composites [15] ; (d) disk milling equipment and SEM photographs of poly(ether ether ketone) before and after pulverization [16] 2 力化学自由基聚合反应 近年来，温度、光、电等外场调控的新型聚合技术兴起引导人们重新认识 机械力 [36,37] 。相较于其他外场调控方式，机械力具有其特殊性，机械力由破坏 性向生产性的转变有利于满足软物质对外力自适应的需求 [11,38] 乙烯基单体逐个与大分子链自由基进行加成反应 [39] 。不饱和单体的自由基聚合 主要通过热活化、光活化 [40,41] 、电活化 [42] 、机械力活化等方式实现，每种活化 方式都有对应的产物结构和单体适用范围。传统自由基聚合通常需要例如偶氮 二异丁氰(AIBN) 、过氧化苯甲酰或烷基硼 [43~45] 等化合物作为聚合反应的引发 剂。然而，在力化学自由基聚合中，这些引发剂不是必须的。 自 Staudinger [15] 发现机械力降解聚合物链的现象以来，机械力对聚合物的 破坏作用被广泛研究。在力化学的发展过程中，研究者发现机械力导致的聚合 物主链共价键均裂会产生具有活性的大分子自由基，这为机械力由破坏性向生 产性的转变提供了可能，并由此建立了高分子力化学与自由基聚合之间的密切 联系。Kargin [46] 在 1959 年首次在振动球磨机中实现了甲基丙烯酸甲酯和苯乙烯 的自由基聚合，带动了学界对力化学自由基聚合的探索。 Oprea 团队 [47] 和 Kuzuya 团队 [48,49] 在无溶剂球磨聚合方向的持续努力将单体的范围扩展至结构多 样的乙烯基单体，如图 2(a)所示，他们认为聚合反应的引发来源于罐体与磨球 剧烈碰撞导致的电子转移。尽管磨具之间剧烈碰撞过程发生的电子转移也是催 化反应和产生自由基的重要途径，但这一过程往往伴随着摩擦热、聚合物降解 和磨具损伤等现象。Kuzuya 团队 [51] 通过无溶剂球磨聚合得到了窄分子量分布的 聚合物。然而，高能球磨降解聚合物的过程广泛存在于力化学自由基聚合反应 的后期，仅得到窄分子量分布的聚合物并不足以说明聚合反应以可控方式进行 (图 2...…”