Synthesis and physical characterization of arborescent (dendrigraft) polymers

树状聚合物的合成和物理表征

• 批准号: RGPIN-2014-03887
• 负责人: Gauthier, Mario
• 金额: $ 3.13万
• 依托单位: University of Waterloo
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2019
• 资助国家: 加拿大
• 起止时间: 2019-01-01 至 2020-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=688718
• 关键词: Synthesis; physical; characterization; arborescent; dendrigraft

Dendritic molecules are characterized by an architecture with multiple branching levels, similar to a tree. These can be subdivided into three distinct families. Dendrimers and hyperbranched polymers are both derived from ABn-type monomers (where functional group A can only react with group B; n = 2 or 3). The perfect structure and uniform size of dendrimers results from strictly controlled cycles of monomer protection, condensation, and deprotection reactions, but an imperfectly branched structure and a broad size distribution often arise when the condensation reaction is carried out without protecting groups. The arborescent (or dendrigraft) polymers, of interest in this proposal, are obtained through successive grafting reactions of linear polymer segments. The growth of these molecules is much faster than for dendrimers over successive generations (reaction cycles), but they display many of their characteristics; they are therefore an interesting alternative to dendrimers for many nanotechnology applications.*This proposal concerns the synthesis and the physical characterization of arborescent polymers (AP). These are novel materials, so there is little understanding of the relationships between their structure/composition and their properties. The information derived from the well-defined AP systems will also help improve the understanding of branched polymer systems in general, many of which are of commercial importance. *The first project involves core-shell AP structures with a hydrophobic polypeptide core and a shell of hydrophilic segments. The research will focus on the solubilization and release properties of these amphiphiles for different model hydrophobes as a function of the structure (branching density, size) and composition of the AP molecules. This will also provide information on the morphology of the AP molecules (extent of phase separation between the core and shell).*In the second project the formation of metallic nanoparticles by AP copolymers with core-shell (CS) and core-shell-corona (CSC) architectures, containing metal-binding poly(2-vinylpyridine) segments, will be examined. We recently observed the formation of intriguing nanomorphologies constrained within the individual AP molecules upon the introduction of metallic ions. These nanostructures likely arise from large differences in interaction (chi) parameter between the metal-rich and metal-poor regions, but their consequences on the physicochemical properties of these hybrid materials are hitherto unexplored. We will examine the formation of these nanostructured materials in a systematic fashion, and ultimately their catalytic properties. The CSC systems display many interesting properties, but their synthesis is very time-consuming and is marred by low yields. We just started investigating a new strategy for the synthesis of these materials, by self-assembly of an AP core-shell structure with a block copolymer where one of the blocks can bind with the AP substrate. This approach looks very promising, but again there is no clear understanding of the rules (thermodynamics) governing this self-assembly process. These will be explored through systematic variations in the structure (e.g. binding block and AP substrate size) of the components and the conditions (solvent, temperature) used.*Finally, to pursue our efforts in developing new methods for the synthesis of AP structures, we will combine a "click" grafting technique which we just developed with atom transfer radical polymerization (ATRP) to considerably expand the range of arborescent polymer compositions available. We will also explore methods for the synthesis or arborescent polybutadiene structures with long side chains, since these are of interest as model highly branched polymer systems.

树突分子的特征是具有多个分支水平的结构，类似于树。它们可以细分为三个不同的科。树状大分子和超支化聚合物都来源于abn型单体（其中A官能团只能与B官能团反应，n = 2或3）。枝状大分子完美的结构和均匀的尺寸是严格控制单体保护、缩合和脱保护反应周期的结果，但在没有保护基团的缩合反应中，枝状大分子的支链结构不完美，尺寸分布广泛。在这个提议中感兴趣的树状（或枝状）聚合物是通过线性聚合物段的连续接枝反应得到的。在连续几代（反应周期）中，这些分子的生长速度比树状大分子快得多，但它们显示出许多树状大分子的特征；因此，在许多纳米技术应用中，它们是树状大分子的有趣替代品。*本提案涉及树状聚合物（AP）的合成和物理表征。这些都是新型材料，因此对其结构/组成与性能之间的关系了解甚少。从定义良好的AP体系中获得的信息也将有助于提高对支链聚合物体系的理解，其中许多具有商业重要性。*第一个项目涉及具有疏水多肽核和亲水段壳的核壳AP结构。本研究将重点研究两亲体对不同模型疏水分子的增溶和释放特性与AP分子结构（分支密度、大小）和组成的关系。这也将提供有关AP分子形态的信息（核和壳之间相分离的程度）。*在第二个项目中，将研究含有金属结合聚（2-乙烯吡啶）片段的AP共聚物与核-壳（CS）和核-壳-电冕（CSC）结构形成的金属纳米粒子。我们最近观察到在引入金属离子后，在单个AP分子内形成了有趣的纳米形态。这些纳米结构可能是由富金属区和贫金属区之间相互作用（chi）参数的巨大差异引起的，但它们对这些杂化材料的物理化学性质的影响迄今尚未被探索。我们将以系统的方式研究这些纳米结构材料的形成，并最终研究它们的催化性能。CSC体系显示出许多有趣的性质，但它们的合成非常耗时且产率低。我们刚刚开始研究一种合成这些材料的新策略，通过用嵌段共聚物自组装AP核壳结构，其中一个嵌段可以与AP底物结合。这种方法看起来很有希望，但是对于控制这种自组装过程的规则（热力学）仍然没有明确的理解。这些将通过组件的结构（例如结合块和AP衬底尺寸）和使用的条件（溶剂，温度）的系统变化来探索。*最后，为了继续努力开发合成AP结构的新方法，我们将把我们刚刚开发的“点击”接枝技术与原子转移自由基聚合（ATRP）相结合，以大大扩大可用的树状聚合物组合物的范围。我们还将探索具有长侧链的树状聚丁二烯结构的合成方法，因为这些结构是高支化聚合物体系的模型。