Rapid production of block copolymer nano-objects via continuous-flow ultrafast RAFT dispersion polymerisation
Rapid production of block copolymer nano-objects via continuous-flow ultrafast RAFT dispersion polymerisation
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DOI：
10.1039/d0py00276c
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发表时间：
2020-05-28
影响因子：
4.6
通讯作者：
Warren, Nicholas J.
中科院分区：
文献类型：
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作者：
Parkinson, Sam;Knox, Stephen T.;Warren, Nicholas J.
在分散聚合条件下利用超快RAFT聚合来合成聚（二甲基丙烯酰胺）-b-聚（二丙酮丙烯酰胺）（PDMAmx-b-PDAAm（y））二嵌段共聚物纳米颗粒。该过程在连续流动反应器中进行，该反应器非常适合快速反应，并且可以容易地消散使该过程具有潜在可扩展性的杂质。通过低场流动核磁共振光谱（flow-NMR）在线获得的瞬态动力学曲线证实了聚合的快速速率，同时仍保持伪一级动力学。凝胶渗透色谱法（GPC）报道了一系列PDMAmx-b-PDAAm（y）二嵌段共聚物（x = 46或113; y = 50、75、100、150和200）的摩尔质量分散度，D <1.3，证实保持了对分子量的控制。通过动态光散射（DLS）和透射电子显微镜（TEM）进行的颗粒表征表明在90 ℃下成功制备了球体和大部分蠕虫相，但仅在70 ℃下才可能形成囊泡形态。为了在该较低温度下保持快速反应速率，增加引发剂浓度，这也是克服氧气逐渐进入PFA管中所需的，氧气逐渐进入PFA管在低自由基浓度下淬灭反应。在接近蠕虫-囊泡边界的PDAAm DP处观察到的不明确的形态，结合摩尔质量分散度的峰，表明不良的混合阻止了这些样品的有效形态转变。然而，通过靶向更高的PDAAm DP，在转变期间存在的额外单体使链塑化以促进在>= 300的PDAAm DP下形成囊泡。
Ultrafast RAFT polymerisation is exploited under dispersion polymerisation conditions for the synthesis of poly(dimethylacrylamide)-b-poly(diacetoneacrylamide) (PDMAmx-b-PDAAm(y)) diblock copolymer nanoparticles. This process is conducted within continuous-flow reactors, which are well suited to fast reactions and can easily dissipate exotherms making the process potentially scalable. Transient kinetic profiles obtained in-line via low-field flow nuclear magnetic resonance spectroscopy (flow-NMR) confirmed the rapid rate of polymerisation whilst still maintaining pseudo first order kinetics. Gel permeation chromatography (GPC) reported molar mass dispersities, D < 1.3 for a series of PDMAmx-b-PDAAm(y) diblock copolymers (x = 46, or 113; y = 50, 75, 100, 150 and 200) confirming control over molecular weight was maintained. Particle characterisation by dynamic light scattering (DLS) and transmission electron microscopy (TEM) indicated successful preparation of spheres and a majority worm phase at 90 degrees C but the formation of vesicular morphologies was only possible at 70 degrees C. To maintain the rapid rate of reaction at this lower temperature, initiator concentration was increased which was also required to overcome the gradual ingress of oxygen into the PFA tubing which was quenching the reaction at low radical concentrations. Ill-defined morphologies observed at PDAAm DPs close to the worm-vesicle boundary, combined with a peak in molar mass dispersity suggested poor mixing prevented an efficient morphological transition for these samples. However, by targeting higher PDAAm DPs, the additional monomer present during the transition plasticises the chains to facilitate formation of vesicles at PDAAm DPs of >= 300.