Sustainable Polymers from Native Silicon

在化学系大分子、超分子和纳米化学项目的资助下，斯蒂芬·A·佛罗里达大学的米勒正在用二氧化硅（氧化硅和沙子）和来自可再生生物质原料的有机分子制造可持续的聚合物。 当今社会的商品塑料主要来自化石燃料，含有高达80%的碳。 这与地壳的元素组成不一致，地壳中只含有0.02%的碳。 这项工作的重点是使用二氧化硅，其中包括近60%的陆地环境，以制备大规模的聚合物。 有针对性的聚合策略包括多次添加硅/氧基结构单元，以形成硅和氧含量在38%至60%之间的延伸聚合物链。 这类新型聚合物产生具有新特性的材料，并为调节这些聚合物使其易于环境降解提供了机会。 与该奖项相关的研究为下一代科学家提供了坚实的培训基础。 该项目为学生准备了一个遵循可持续发展原则的世界。这项研究涵盖了各种可持续性指标。 将廉价的二氧化硅纳入商品塑料中可以加速可持续聚合物的发展并拓宽材料应用的种类。米勒教授和他的研究团队继续坚定地致力于培训和指导本科生，其中许多人是化学中代表性不足的群体的成员。 本研究的重点是直接转化天然二氧化硅和生物基二醇离散烷基原硅酸酯单体。 二氧化硅解聚策略特别避免了昂贵的氧化还原化学，并使用改进的相转移催化剂与高温、微波或超声处理相结合进行优化。 直接单体聚合或正硅酸烷基酯复分解聚合（ASMP）使聚酯、聚碳酸酯、聚缩醛、聚酰胺和聚酰亚胺的硅+氧含量在38%至60%之间。 这些新型聚烷基原硅酸盐的制备和表征揭示了对基本聚合物结构/性能关系的洞察，沿着对如何操纵硅-氧键的更好理解，尽管硅-氧键在地壳中无处不在，但它是神秘的。 合成的聚正硅酸烷基酯具有新的材料性能，包括那些受到非常强的硅-氧键影响的性能。 此外，将硅-氧键限制在环上有望将玻璃化转变温度提高到高温包装塑料的范围内。 虽然分子烷基原硅酸盐在数小时内水解，但嵌入相对疏水聚合物中的该官能团的水解预计较慢且可调。 与聚正硅酸烷基酯水解过程中的速率、途径和降解产物相关的系统研究可以促进环境降解。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

With funding from the Macromolecular, Supramolecular and Nanochemistry Program of the Chemistry Division, Professor Stephen A. Miller of University of Florida is building sustainable polymers from silica (silicon oxide and sand) and organic molecules derived from renewable biomass feedstocks. Commodity plastics in today's society are largely derived from fossil fuels and contain as much as 80 percent of carbon. This is inconsistent with the elemental composition of earth's crust which contains only 0.02 percent carbon. This work focuses on the use of silica, which comprises nearly 60 percent of the terrestrial environment, to prepare large-scale polymers. Targeted polymerization strategies include multiple additions of silicon/oxygen based building blocks to form extended polymer chains with the content of silicon and oxygen ranging between 38 and 60 percent. This novel class of polymers yields materials with new properties and provides opportunities for tuning these polymers toward easy environmental degradation. The research associated with this award provides a solid training ground for the next generation of scientists. The project prepares the students for a world which follows the principles of sustainability. This research embraces various sustainability metrics. The inclusion of inexpensive silica into commodity plastics could accelerate the growth of sustainable polymers and widen the variety of materials applications. Professor Miller and his research team continue their strong commitment to training and mentoring of undergraduate students, many of whom are members of underrepresented groups in chemistry. This research focuses on the direct conversion of native silica and biobased diols to discrete alkylorthosilicate monomers. The silica depolymerization strategy specifically avoids costly redox chemistry and is optimized with improved phase transfer catalysts, in combination with elevated temperature, microwaves, or sonication. Direct monomer polymerization or alkylorthosilicate metathesis polymerization (ASMP) renders polyesters, polycarbonates, polyacetals, polyamides, and polyimides with a silicon+oxygen content ranging between 38 and 60 percent. Preparation and characterization of these novel polyalkylorthosilicates reveal insight into fundamental polymer structure/property relationships, along with improved understanding of how to manipulate the silicon-oxygen bond, which is enigmatic despite its ubiquity in the earth's crust. The synthesized polyalkylorthosilicates possess new material properties, including those impacted by the very strong silicon-oxygen bond. Additionally, confining the silicon-oxygen bond to a ring is expected to improve the glass transition temperature into the range of high-temperature packaging plastics. While molecular alkylorthosilicates are hydrolyzed over the course of hours, the hydrolysis of this functional group embedded in relatively hydrophobic polymers is predicted to be slower and tunable. Systematic studies associated with rates, pathways, and degradation products during polyalkylorthosilicate hydrolysis could enable facile environmental degradation.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.