吡咯衍生物／吡咯之共聚物製備及其電化學性質之研究

Preparation and Electrochemical Properties of N-substituted Pyrrole/Pyrrole Copolymers

李俊龍(Chun-Lung Li)

指導教授 ： 陳玉惠

中原大學/理學院/化學研究所/博士(2004年)

https://doi.org/10.6840/cycu200400140

摘要

本研究首先合成四種吡咯（Pyrrole，Py）衍生物，分別為N-(2-hydroxyethyl)pyrrole (HE)、N-(3-hydroxypropyl)pyrrole (HP)、N-(2-carboxyethyl)pyrrole (CE)與N-(5-carboxypentyl)pyrrole (CP)，以NMR及FTIR確認其結構。利用這四種pyrrole衍生物以定電流聚合法製備其單聚物及吡咯／衍生物之共聚物，以FTIR及EA確認其共聚物結構與組成，並以TGA、DSC、SEM、CV…等測量其相關性質。
定電流聚合的時間-電壓圖顯示，取代基會產生立體障礙使電聚合過程中之三個聚合階段的完成時間與電壓增加；但共聚合反應中因Py單體的添加使立體障礙獲得改善，而顯示出與Py相似的時間-電壓圖。TGA結果顯示PPy之T5%為248.7 ℃，而衍生物單聚物之耐熱性不佳，其T5%介於100～150 ℃之間；共聚物之T5%則均在200 ℃左右，介於PPy及相對應的衍生物單聚物之間。由DSC結果顯示單聚物均有明顯的Tg點，且受氫鍵作用力影響其Tg會上升，而較長鏈的取代基會在高分子主鏈間造成較大的自由體積(Free volume)，又會使Tg下降；各系列共聚物受到Ramdon結構的影響，其Tg點顯得不明顯而無法判斷。部分聚合物之SEM影像呈現平坦的表面型態，顯示其以2D的成長機制進行聚合；其它聚合物則以3D的機制聚合成長，而呈現顆粒狀堆積的粗糙表面形態，表示聚合成長機制會受到取代基的影響，而取代基上的官能基種類亦是決定機制的重要因素之一。
經導電度測試得到PPy導電度為14.5 S/cm，而單聚物會因取代基的空間效應，造成主鏈共平面結構的扭曲，使導電度顯著下降；但也因Py重複單位的存在，取代基的空間效應減弱，大部分共聚物的導電度僅略低於PPy。此外，衍生物單聚物具有比PPy更好的抗腐蝕特性，尤其是hydroxy單聚物；而共聚物之抗腐蝕特性雖隨Py量增加而衰減，但仍比PPy佳。
循環伏安圖顯示各系列間單聚物的氧化還原電流大小排序為 carboxy > PPy > hydroxy，代表不同種類官能基對離子的作用力強度不同；由於hydroxy單聚物會與離子產生較強的作用力，導致移動速率下降而減低氧化還原的電流量。共聚物中取代基密度因Py單位的存在而降低，離子的牽制力因而獲得改善，使離子的移動速度提升，造成氧化還原電流上升；亦使共聚物之比電荷儲存量隨之增加，且比PPy高2～7.5倍。
Py單體添加量80 %所獲得之共聚物，具有同系列中最高的平均電容量，且高於PPy；比較第二十次之充放電電容量，顯示Py含量較高的共聚物可獲得比PPy高的充放電電容量，而本論文中以CP系列之PYCP82共聚物具有最高電容量。綜合以上結果顯示取代基可提升離子在pyrrole聚合物中的移動速率，進而增加充放電電容量。

關鍵字

電化學 ； 衍生物 ； 聚吡咯 ； 導電高分子 ； 循環伏安

並列摘要

In this study, four derivatives of pyrrole (Py), N-(2-hydroxyethyl) pyrrole (HE), N-(3-hydroxypropyl) pyrrole (HP), N-(2-carboxyethyl) pyrrole (CE) and N-(5-carboxypentyl) pyrrole (CP), were synthesized. Their homopolymers, PHE, PHP, PCE and PCP, and the corresponding copolymers with Py, PYHE, PYHP, PYCE and PYCP, were prepared by galvanostatic electropolymerization and characterized by 1H-NMR, FTIR and EA measurements.
The result of potential-time profiles indicated that a higher potential was required for derivative monomers than Py for the polymerization. This was ascribed to the steric hindrance of high concentration of the N-substituent groups. However, a similar profile was observed for the copolymerization of Py/derivative systems as that of Py due to the reduction of the steric effect by lower content of the substituent. The TGA thermograms showed that all the polymers were thermally stable up to 130 oC and the decomposition temperature of the copolymers occured between those of PPy and the corresponding homopolymers. All the homopolymers showed glass transition temperature (Tg) in DSC thermograms and the presence of long alkyl side chain makes lower Tg that indicates having larger free volume between polymer chain. The identification of Tg of copolymers was difficult, it may be due to their random structures. There are few polymers that polymerized under two-dimensional growth mechanism and showed smoothly morphologies in SEM micrographs. The other polymers polymerized under three-dimensional growth mechanism and showed globular roughly morphologies. This indicates that growth mechanisms would also be affected with different types of functional groups.
Though the derivative polymers have lower conductivity than PPy, but they have better corrosion properties than PPy, especially homopolymers.
The cyclic voltammograms of all polymers are quasi-reversible type electrochemical behavior; moreover, PPy and copolymers showed good cycling stability. The cyclic voltammograms indicated that all the copolymers were larger, while the homopolymers had smaller anodic/cathodic currents and specific charge storages than PPy. This implied that the existence of the proper amount of the N-substituted pendant groups enhanced the ionic mobility in the PPy-based polymers. In addition, the order of redox current of homopolymers are carboxy > PPy > hydroxy that represents hydroxy group having stronger interaction with ions than others. The response of charge/discharge measurements showed the copolymers, which prepared with 80 % Py monomer, having the highest average capacities in each system, even higher than PPy. The copolymers which content higher Py units in each systems show higher capacities than PPy at the 20th cycle and the highest capacity was obtained in CP system. As discussed above, functionalized N-substituted pendent groups can improve the ionic mobility in polymer films that enhancing redox current, specific charge storage and charge/discharge capacity.

並列關鍵字

polypyrrole ； derivative ； electrochemistry ； CV ； conducting polymer

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