利用分子動力學開發兼具耐高溫及優良機械性質之可回收生物基環氧樹脂

Abstract

在全球日益重視環境永續與循環經濟的背景下，可回收高性能材料的開發成為高分子科學中亟需突破的課題，環氧樹脂因其優異的熱穩定性與機械強度廣泛應用於電子、航太及複合材料領域，然其難以降解的交聯網狀結構亦造成嚴重環境負擔。為此本研究從分子結構設計出發，透過材料改質並結合分子動力學模擬，系統性探討材料結構對降解行為及熱、機械性質的綜合影響，期望提出兼具高性能與具可回收性的環氧材料設計新思維。本研究以具剛性芳香環結構的香草醛為改質基礎，設計出Vanillin-Epoxy 4 (V-EP4)與Vanillin-Epoxy 2 (V-EP2)兩種分別具有高、低立體位障結構之環氧單體，並搭配None、Carbonyl (C)、Sulfone (S)三種固化劑以調控反應位點電子密度，藉由調控環氧樹脂自身立體位障與反應位點電子密度，系統性分析材料結構對降解速率、熱與機械性質的影響。首先透過Electrostatic potential (ESP)計算，我們知道了以碸基改質之固化劑S可有效降低羧基反應位點的電子密度，其次是以羰基改質之C，最後則是未額外引入幫助降解官能基之None。在降解速率部分，透過分子動力學模擬以溶劑乙二醇降解環氧樹脂之過程並計算其中溶劑消耗速率，在V-EP4系統中，降解速率最快之系統為V-EP4-C，其次是V-EP4-S，V-EP4-None則明顯慢於前兩者，因此我們發現引入具有拉電子效應的羰基與碸基確實能顯著提升降解速率，然而碸基亦因其較大的立體位障阻礙了溶劑滲透，使其降解速率並不如預期般大幅提升，此推論在V-EP2系統得到證實，在位障較低的情況下V-EP2-S降解速率最快，V-EP2-C次之，V-EP2-None最慢。在熱與機械性質方面，V-EP4系列之性能已超越DGEBA系統的平均值，其中最出色的為V-EP4-S，楊氏模量達3.7 GPa，玻璃轉化溫度更是達623.5 K，已接近目前已發表環氧樹脂文獻的最高紀錄，而在V-EP2系列中，儘管整體性能稍弱，V-EP2-S系統仍維持楊氏模量3.1 GPa與玻璃轉化溫度489.8 K，表現依然優於DGEBA系統平均值，突顯其在確保快速降解前提下仍具備實用性，顯示本研究提出的可降解生物基改質策略能有效賦予材料卓越性能。本研究開創性的探討反應位點電子密度與立體位障對環氧樹脂系統降解速率及熱、機械性質與材料結構的關係，為可回收高性能環氧樹脂之分子設計提供明確方向，在材料性能與永續發展兩大核心議題間取得平衡，期望能在達成生物與環境友善的同時，賦予環氧樹脂實質應用潛力。

Amid growing global emphasis on environmental sustainability and the circular economy, developing recyclable high-performance materials has become a pressing challenge in polymer science. Epoxy resins are widely applied in electronics, aerospace, and composites due to their excellent thermal and mechanical properties, yet their non-degradable crosslinked networks cause serious environmental issues. To address this issue, this study starts from molecular structure design, incorporating material modification and molecular dynamics (MD) simulations to systematically investigate the combined effects of material structure on degradation behavior, thermal stability, and mechanical properties. Based on vanillin, two epoxy monomers (V-EP4 and V-EP2) with varying steric hindrance were designed, along with three curing agents (None, C, S) to modulate the electron density at the reactive sites. Electrostatic potential (ESP) calculations revealed that S and C substituents significantly reduce electron density. Through MD simulations using ethylene glycol as the degrading solvent, we found that introducing electron-withdrawing groups such as carbonyl and sulfone markedly increased degradation rates. However, the bulky sulfone group also hindered solvent penetration due to steric hindrance, limiting its rate-enhancing effect. In terms of performance, V-EP4-S showed a Young’s modulus of 3.7 GPa and Tg of 623.5 K, close to the highest reported values, while V-EP2-S still surpassed DGEBA averages, demonstrating both fast degradability and practical applicability. This study provides a clear molecular design direction by revealing how electron density and steric hindrance affect degradation rate, thermal and mechanical properties, offering a balance between performance and sustainability and highlighting the practical potential of recyclable, bio-based epoxy resins.