具有多孔结构的无机粒子亲CO2修饰及在聚合物scCO2微孔发泡中成核机理研究

For the polymeric microcellular foams, the addition of iorganic particles that are able to act as the heterogeneous nucleant is a commonly used method to increase the cell density and improve the morphologies and properties of the foams. However, the nucleation efficiency of these particles is low, and the mechanism of the heterogeneous nucleation remains to be further elucidated. To solve these problems, we propose to study the nucleation effect of the particle with a specifically porous stucture on the polymer microcullar foaming using scCO2 as the blowing agent. Due to the high specific surface area and CO2-philic modification of the cavities, scCO2 can be enriched inside the porous particle. Additionally, the cavities on particle surface will form caviary structure and special wetability with polymer matrix. The locally concentated blowing agent and cavitary structure will significantly increase the heterogeneous nucleation efficiency of the particles. The influences of the blowing agent localization, cavitary morphology, wetability and other factors on the nucleation efficiency, as well as the heterogeneous nucleation machanism of these particles with specifically porous stucture will be systematically studied. In this project, to have a further insight into the nucleation mechanism of the porous particles, we also propose the study using an anodic aluminum oxide (AAO) film as sbustrate to prepare complex architectures with polymer. Through the complex stucture, a lot of structual parameters such as cave size, contact angle can be quantitatively characterized. The study on the nucleation in the interfacial region of the complex stucture will offer us a new insight into the mechanism of the hetergeneous nucleation, and thus a model about the nucleation can be established. The research of this project will not only unveil the nucleation mechanism of the particles with porous structure and provide a new idea to increase the nucleation efficiency of the inorganic particles, but also provide a new methodology for the study of the heterogeneous necleation in polymer micraocellular foaming. Therefore, it has significantly scientific and application values.

对于聚合物微孔发泡材料，引入无机粒子作为异相成核剂是提高泡孔密度、改善泡孔结构以及材料性能的重要手段。但无机粒子成核效率低、成核机理还有待深入研究是该领域存在的主要问题。针对上述问题，本项目提出以具有特定孔结构的无机粒子为异相成核剂，通过其孔道结构大比表面积及亲CO2修饰实现scCO2的富集，同时利用其多孔形貌构建空穴结构以及实现与聚合物特殊的润湿作用，提高异相成核效率，研究发泡剂富集、空穴结构、润湿性等因素对异相成核的作用规律，探索成核机理。为进一步研究多孔粒子的成核机理，同时提出以阳极氧化铝膜为基材与聚合物构建复合体系，实现各种结构参数的定量表征，通过研究界面处成核过程深入地研究异相成核机理，建立相关理论模型。本项目不仅将揭示具有特定孔结构无机粒子的异相成核机理，为如何提高无机粒子的异相成核效率提供新的思路，还为异相成核机理的研究提供新的模型方法，对该领域具有重要的理论意义和实用价值。

无机粒子用于聚合物超临界二氧化碳（scCO2）微孔发泡改善泡孔结构同时赋予材料新的功能是聚合物发泡材料的一个重要研究方向，如何提高无机粒子的异相成核效率，揭示成核机理是本领域的关键科学问题。本项目设计并合成了一类具有多孔结构的无机粒子，通过改变原料组成、反应条件等实现了粒子形貌、孔道结构的调控，采用功能硅烷偶联剂、离子液体、离子液体聚合物等对孔道和粒子表面进行了亲二氧化碳修饰，进一步将其用于聚合物scCO2微孔发泡中，系统考察了粒子结构、亲二氧化碳修饰、与聚合物基体浸润及“气穴”结构等对scCO2富集和异相成核的影响规律。研究发现，多孔粒子能够与聚合物基体形成气穴结构，同时在孔道内部实现二氧化碳富集，从而降低了聚合物在发泡过程中的成核能垒，具有优异的异相成核作用。多孔粒子的异相成核效率与粒子形貌、孔道结构和表面改性密切相关。项目发现，多孔粒子尺寸越小、孔道尺寸越大，其异相成核效率越高；在改性方面，小分子硅烷改性能够有效的保留孔道结构，有助于scCO2的富集，采用含氟硅烷改性多孔粒子，在保留孔道和富集二氧化碳的同时，与聚合物基体形成最优的相互作用和“气穴”结构，具有更高的异相成核效率。作为成核机理的深入探讨，项目还以具有多孔结构的阳极氧化铝膜（AAO）为基材，通过研究聚合物与AAO膜界面处成核过程考察多孔粒子的成核机理。结果表明，AAO膜能够模拟多孔粒子表面，界面处成核点多，泡孔尺寸小、密度高，同样随着孔道尺寸的增加异相成核效率明显提高。在此基础上，项目还发现该方法能够制备具有泡孔尺寸呈完美梯度变化的多级发泡材料，特别是聚乳酸发泡材料，梯度变化的范围可达1mm以上，在吸音降噪、电磁屏蔽、组织工程等领域具有重要的应用价值。本项目的研究揭示多孔粒子在聚合物scCO2微孔发泡中异相成核作用的关键因素，阐明了相关机理，并建立了一种制备梯度泡孔结构发泡材料的新方法，无论对高效成核剂的开发和应用还是聚合物发泡材料的高性能化和功能化均具有重要理论意义和应用价值。