分子動力學模擬探討苯酚幾丁聚醣之苯酚取代度對其自癒合水膠結構與性質之影響

Abstract

苯酚幾丁聚醣是以幾丁聚醣為基礎，添加了苯酚衍生物的一種高分子，苯酚基團可以破壞幾丁聚醣的分子間和分子內氫鍵，從而降低其結晶度並提高其水溶性，由於苯酚幾丁聚醣有良好的多種生理功能，近年來備受關注，尤其在點擊化學製備的水膠中，常常利用席夫鹼反應來合成苯酚幾丁聚醣水膠。然而，目前尚不清楚苯酚幾丁聚醣中苯酚取代程度是否影響自癒合水膠的分子相互作用和結構特性，為了探討這個問題，我們利用分子動力學模擬研究由不同苯酚取代度的苯酚幾丁聚醣和雙苯甲醛聚乙二醇(DB-PEO)組成的自癒合水膠網絡與其結構特性。通過對研究結果的分析，本研究表明自癒合水膠的苯酚取代度低於15%時，苯酚取代度的增加導致苯酚幾丁聚醣和DB-PEO之間的相互作用增加，並增強了席夫鹼動態交聯，也知道水膠在自癒合後可以完全恢復到初始的狀態，並且苯酚幾丁聚醣和DB-PEO的分子間能量不變，水膠的構型依然穩定。然而，當苯酚取代度超過15%時，過多的苯酚基團導致苯酚幾丁聚醣分子內過度的相互作用，從而降低了苯酚幾丁聚醣與DB-PEO之間的結合，而水膠在自癒合後雖然也能完全恢復到初始的狀態，但苯酚幾丁聚醣和DB-PEO的分子間能量有明顯的下降，表示苯酚取代度過高會影響到水膠的結構。我們的結果揭示了苯酚取代度對自癒合水膠分子結構的影響，並表明存在最佳的苯酚取代度。這些發現為未來基於幾丁聚醣的自癒合水膠的設計提供了重要的見解，並將有助於增強水膠在生物醫學領域的適用性。

Chitosan-phenol is a polymer based on chitosan with the addition of phenol derivatives. The phenol groups can disrupt the intermolecular and intramolecular hydrogen bonds of chitosan, thereby reducing its crystallinity and increasing its water solubility. Due to its various physiological functions, chitosan-phenol has gained significant attention in recent years, particularly in the preparation of click chemistry-based hydrogels where Schiff base reaction is often used to synthesize chitosan-phenol hydrogels. However, it is currently unclear whether the phenol substitution degree in the main chain of chitosan-phenol affects the molecular interactions and structural properties of self-healing hydrogels. To investigate this issue, we conducted molecular dynamics simulations to study the self-healing hydrogel network composed of chitosan-phenol with different phenol substitution degrees and dibenzaldehyde polyethylene oxide (DB-PEO), and examined their structural properties. Through the analysis of the research results, this study demonstrates that when the phenol substitution degree in the self-healing hydrogel is below 15%, an increase in the phenol substitution degree leads to increased interactions between chitosan-phenol and DB-PEO, enhancing the Schiff base dynamic crosslinking. It is also observed that the hydrogel can fully recover to its initial state after self-healing, and the intermolecular energy between chitosan-phenol and DB-PEO remains unchanged, indicating a stable configuration of the hydrogel. However, when the phenol substitution degree exceeds 15%, excessive amount of phenol groups leads to excessive intramolecular interactions within chitosan-phenol molecules, which reduces the binding between chitosan-phenol and DB-PEO. Although the hydrogel can still fully recover to its initial state after self-healing, there is a significant decrease in the intermolecular energy between chitosan-phenol and DB-PEO, indicating that a high phenol substitution degree can affect the structure of the hydrogel. Our results reveal the influence of the phenol substitution degree on the molecular structure of self-healing hydrogels and indicate the existence of an optimal phenol substitution degree. These findings provide important insights for the future design of self-healing hydrogels based on chitosan and contribute to enhancing the applicability of hydrogels in the field of biomedicine.