具有定制接枝分布的聚合物的设计、合成和自组装,Journal of the American Chemical Society

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具有定制接枝分布的聚合物的设计、合成和自组装
Journal of the American Chemical Society ( IF 14.4 ) Pub Date : 2017-11-20 , DOI: 10.1021/jacs.7b10525
Alice B. Chang ₁ , Tzu-Pin Lin ₁ , Niklas B. Thompson ₁ , Shao-Xiong Luo ₁ , Allegra L. Liberman-Martin ₁ , Hsiang-Yun Chen ₁ , Byeongdu Lee ₂ , Robert H. Grubbs ₁

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接枝密度和接枝分布影响聚合物的链尺寸和物理性质。然而，实现对这些结构参数的精确控制提出了长期存在的合成挑战。在本报告中，我们介绍了一种通用策略，通过接枝开环复分解聚合 (ROMP) 来合成具有定制结构的聚合物。ω-降冰片烯基大分子单体和离散的降冰片烯基共聚单体（稀释剂）的一锅共聚提供了控制主链序列和侧链分布的机会。为了序列控制，研究了 23 种稀释剂的均聚动力学，代表立体化学、锚定基团和取代基的不同变化。这些修改将均聚速率常数调整了 2 个数量级 (0. 36 M-1 s-1 < khomo < 82 M-1 s-1)。通过补充机制和密度泛函理论 (DFT) 研究确定和阐明速率趋势。在此基础上，通过选定稀释剂与聚 (d,l-丙交酯) (PLA)、聚二甲基硅氧烷 (PDMS) 或聚苯乙烯 (PS) 大分子单体的共聚，实现了复杂的结构。根据 Mayo-Lewis 终端模型，通过瞬时共聚单体浓度的非线性最小二乘拟合获得交叉传播速率常数。深入的动力学分析表明，大分子单体/稀释剂反应性比率范围很广（0.08 < r1/r2 < 20），对应于块状、梯度或随机骨架序列。我们通过合成具有锥形、均匀和倒锥形分子“形状”的 AB 接枝二嵌段聚合物，进一步证明了这种共聚方法的多功能性。自组装结构的小角度 X 射线散射分析说明了接枝分布对域间距和骨架构象的影响。总的来说，本文提供的对 ROMP 机制、单体设计以及均聚和共聚速率趋势的见解为具有任意结构的接枝聚合物的设计和合成提供了通用策略。因此，受控共聚扩展了分子和材料设计的参数空间。自组装结构的小角度 X 射线散射分析说明了接枝分布对域间距和骨架构象的影响。总的来说，本文提供的对 ROMP 机制、单体设计以及均聚和共聚速率趋势的见解为具有任意结构的接枝聚合物的设计和合成提供了通用策略。因此，受控共聚扩展了分子和材料设计的参数空间。自组装结构的小角度 X 射线散射分析说明了接枝分布对域间距和骨架构象的影响。总的来说，本文提供的对 ROMP 机制、单体设计以及均聚和共聚速率趋势的见解为具有任意结构的接枝聚合物的设计和合成提供了通用策略。因此，受控共聚扩展了分子和材料设计的参数空间。

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Design, Synthesis, and Self-Assembly of Polymers with Tailored Graft Distributions

Grafting density and graft distribution impact the chain dimensions and physical properties of polymers. However, achieving precise control over these structural parameters presents long-standing synthetic challenges. In this report, we introduce a versatile strategy to synthesize polymers with tailored architectures via grafting-through ring-opening metathesis polymerization (ROMP). One-pot copolymerization of an ω-norbornenyl macromonomer and a discrete norbornenyl comonomer (diluent) provides opportunities to control the backbone sequence and therefore the side chain distribution. Toward sequence control, the homopolymerization kinetics of 23 diluents were studied, representing diverse variations in the stereochemistry, anchor groups, and substituents. These modifications tuned the homopolymerization rate constants over 2 orders of magnitude (0.36 M-1 s-1 < khomo < 82 M-1 s-1). Rate trends were identified and elucidated by complementary mechanistic and density functional theory (DFT) studies. Building on this foundation, complex architectures were achieved through copolymerizations of selected diluents with a poly(d,l-lactide) (PLA), polydimethylsiloxane (PDMS), or polystyrene (PS) macromonomer. The cross-propagation rate constants were obtained by nonlinear least-squares fitting of the instantaneous comonomer concentrations according to the Mayo-Lewis terminal model. In-depth kinetic analyses indicate a wide range of accessible macromonomer/diluent reactivity ratios (0.08 < r1/r2 < 20), corresponding to blocky, gradient, or random backbone sequences. We further demonstrated the versatility of this copolymerization approach by synthesizing AB graft diblock polymers with tapered, uniform, and inverse-tapered molecular "shapes." Small-angle X-ray scattering analysis of the self-assembled structures illustrates effects of the graft distribution on the domain spacing and backbone conformation. Collectively, the insights provided herein into the ROMP mechanism, monomer design, and homo- and copolymerization rate trends offer a general strategy for the design and synthesis of graft polymers with arbitrary architectures. Controlled copolymerization therefore expands the parameter space for molecular and materials design.

更新日期：2017-11-20

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