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乙烯基膦酸二乙酯與2-氨基苯並咪唑的化學反應

納爾基斯  

含磷聚合物因其在燃料電池、阻燃劑和生物醫學領域的廣泛應用而特別有吸引力。含磷聚合物包括遺傳物質DNA和RNA，以及主鏈官能化和側鏈官能化的合成聚合物。乙烯基膦酸酯是最簡單的乙烯基單體之一，側鏈帶有膦酸酯基團。自 20 世紀 40 年代末期以來，已有不同的乙烯基膦酸酯合成路線被報導。在這些技術中，配位陰離子聚合和活性稀土金屬介導的基團轉移聚合可有效產生具有較高分子量和較高轉化率的聚（乙烯基膦酸酯）。除了聚乙烯基膦酸（可以透過自由基聚合以高產率和中等分子量獲得）之外，透過自由基聚合對乙烯基膦酸酯單體進行均聚和共聚的研究相對較少。少數報告表明，乙烯基膦酸酯單體無法透過自由基聚合的方法（特別是乙烯基膦酸二乙酯（DEVP））均聚成高分子量產物，這通常導致產率低且提供低分子量的聚合物。在自由基共聚的情況下，最終結果要么不成功，要么沒有提供足夠的表徵。 Arcus 報告了叔丁基過氧化氫引發的 DEVP 與苯乙烯的共聚，並確定了此單體對的反應活性比。由於共聚物中 DEVP 含量相對較低，與苯乙烯相比，DEVP 不願意進入成長的聚合物鏈。除苯乙烯外，DEVP 與乙二醇二甲基丙烯酸酯、甲基丙烯酸甲酯、丙烯腈和三甲氧基乙烯基矽烷均實現了自由基共聚，但表徵不充分。因此，DEVP與其他單體的自由基共聚以獲得具有清晰結構的相對高DEVP含量的共聚物仍然是一個重要且具有挑戰性的問題。

Poly(diethyl vinylphosphonate-co-2-chloroethyl methacrylate) (P(DEVP-co-CEMA)) copolymers are synthesized by free radical copolymerization initiated by benzoyl peroxide. The reactivity ratios for the free radical copolymerization of CEMA (M1) and DEVP (M2) are r1 = 19.45 and r2 = 0.11, respectively. The desired amphiphilic copolymers with relatively low polydispersity index (PDI) and different DEVP contents are isolated and purified from the reaction mixtures through precipitation fractionation. The structures and molecular characteristics of the obtained products are characterized by 1 H NMR, FTIR, and SEC analysis. All of these fractionated copolymers have a unimodal distribution and moderate PDI. The thermal properties of the P(DEVP-co-CEMA) copolymers are investigated by TGA and differential scanning calorimetry (DSC) measurements. Single glass transition temperature (Tg) appears in the DSC profiles differing from the existence of two Tgs in the blend of poly (diethyl vinylphosphonate) and poly (2-chloroethyl methacrylate), which indicates the random structure of the copolymers. The MALDI–ToF mass analysis further reveals that DEVP and CEMA units are randomly distributed in the copolymer chains. The self-assembly behavior of the P(DEVP-co-CEMA) copolymers in aqueous solution is preliminarily investigated.

The monomer 2-chloroethyl methacrylate (CEMA) is of special interest as halogen-functionalized comonomer for easy modification and post cross-linking. With initiating haloalkyl groups, graft copolymers can be prepared via atom transfer radical polymerization (ATRP. The chlorine atoms can be readily substituted by nucleophiles, for instance, azide groups, and then followed by click coupling of alkyne end-functionalized polymers to gain new properties. Therefore, CEMA is a potential comonomer for DEVP to broaden the applications of phosphorus-containing polymers. To date, to the best of our knowledge, there is no report on the copolymerization of DEVP with CEMA. What is more, due to the existence of both hydrophobic units (CEMA) and hydrophilic units (DEVP), the copolymers are able to self-assemble into nanoparticles in aqueous solution, which are promising in the fields such as microreactors and encapsulation of guest molecules. The modified copolymers show great potential in biomedical fields for polyphosphonates and proved to be high biocompatibility and adjustable degradability. Meanwhile, the chemical incorporation of a phosphorus-containing flame retardant into a methacrylate polymer via copolymerization may eliminate the leaching and heterogeneous problems associated with the additive approach.

在此，我們以過氧化苯甲醯（BPO）為引發劑，透過自由基共聚合成了一系列兩親性無規共聚物，即聚（乙烯基膦酸二乙酯-co-2-甲基丙烯酸氯乙酯）（P（DEVP-co-CEMA））。透過沉澱分級分離具有相對窄分子量分佈的共聚物以進行詳細研究。共聚物的結構透過 1 H NMR、31P NMR、傅立葉變換紅外線 (FTIR) 和 MALDI-ToF 品質分析得到證實。 P(DEVP-co-CEMA) 共聚物的熱性能透過差示掃描量熱法 (DSC) 和熱重分析 (TGA) 測量來確定。也對共聚物在水中的自組裝行為進行了初步研究，並透過 TEM 觀察了水中形成的奈米顆粒。實驗材料亞磷酸三乙酯（98.0%，阿拉丁試劑，中國）、溴乙烯（99.0%，阿拉丁試劑，中國）、三乙胺（國藥化學試劑，中國）、苯（國藥化學試劑，中國） 、甲基丙烯酰氯（J&K化學試劑） ，中國）和2-氯乙醇（上海南翔試劑，中國）按原樣使用。 BPO（上海凌峰化學試劑，中國）使用前從甲醇中重結晶兩次。使用前將THF經由鉀/二苯甲酮羰基回流。除非另有說明，所有其他化學品均按收到時的原樣使用。 CEMA的合成將2-氯乙醇(10mL)和三乙胺(22mL)溶解在THF(50mL)中，然後在氬氣氛下緩慢加入甲基丙烯酰氯(15mL)，同時在冰浴中冷卻溶液。將反應混合物在室溫下攪拌48小時，然後過濾。