廣東工業(yè)大學(xué)劉曉暄教授團(tuán)隊(duì)在3D打印自修復(fù)功能有機(jī)硅材料領(lǐng)域取得新進(jìn)展

來源：高分子科技

近日，廣東工業(yè)大學(xué)劉曉暄教授高分子光化學(xué)團(tuán)隊(duì)在3D打印自修復(fù)功能有機(jī)硅材料領(lǐng)域取得了階段性進(jìn)展，研究成果以題為“Self-healing, reprocessing and 3D printing of transparent and hydrolysis resistant silicone elastomers”發(fā)表在《Chemical Engineering Journal》。論文的第一作者為廣東工業(yè)大學(xué)博士生劉珠，通訊作者為劉曉暄教授。

在加工和使用過程中，有機(jī)硅材料會(huì)不可避免地遇到微裂紋、開裂等損傷，微裂紋通常很難檢測(cè)，持續(xù)使用會(huì)導(dǎo)致材料的性能下降甚至失效，帶來嚴(yán)重的安全隱患。實(shí)現(xiàn)快速高效固化的同時(shí)，實(shí)現(xiàn)自我修復(fù)并恢復(fù)原有各項(xiàng)性能指標(biāo)，對(duì)提高有機(jī)硅材料的使用壽命及安全性，降低更換成本具有重要意義。目前市面工業(yè)化有機(jī)硅材料還無法實(shí)現(xiàn)光固化，這是因?yàn)闃O性光固化基團(tuán)很難引入聚硅氧烷鏈，制備提純困難，相容性及儲(chǔ)存穩(wěn)定性差。此外，可逆動(dòng)態(tài)鍵一般也具有強(qiáng)極性較難引入聚硅氧烷鏈，而本征型自修復(fù)材料是通過構(gòu)建可逆動(dòng)態(tài)鍵實(shí)現(xiàn)的。為此，目前自修復(fù)有機(jī)硅彈性體較難同時(shí)實(shí)現(xiàn)光固化和自修復(fù)性能，一般采用熱固化方式且制備出的彈性體不透明、相容性差且抗水解性差。因此，基于優(yōu)異抗水解性能的自修復(fù)透明光固化有機(jī)硅材料的研究在3D打印應(yīng)用領(lǐng)域顯得很有意義。

劉曉暄教授團(tuán)隊(duì)通過PDMS–SH與端乙烯硅油的光誘導(dǎo)點(diǎn)擊反應(yīng)及羧基硅油與氨基硅油的熱可逆動(dòng)態(tài)離子交聯(lián)構(gòu)建的可逆/不可逆雜化雙網(wǎng)絡(luò)，制備出一種可快速UV固化及優(yōu)異自修復(fù)性的有機(jī)硅透明彈性體。并將其應(yīng)用于3D打印上，打印出具有優(yōu)異多重自修復(fù)性能的有機(jī)硅彈性體實(shí)體。制備的光-熱雙交聯(lián)有機(jī)硅彈性體的固化機(jī)理及交聯(lián)網(wǎng)絡(luò)示意圖（圖1）。

圖1 Schematic illustration of photo-thermal dual-curing and crosslinked networks of silicone elastomers.

制備的雙交聯(lián)有機(jī)彈性體UV光輻射下，可3 s內(nèi)凝膠，20 s內(nèi)巰基-烯初網(wǎng)絡(luò)基本交聯(lián)完成形成初始強(qiáng)度，且離子交聯(lián)網(wǎng)絡(luò)不影響巰基-烯光固化網(wǎng)絡(luò)的形成，滿足SLA 3D打印的先決條件（圖2）。

圖2 (a) G' and G'' during in situ rheological test; (b) real-time infrared spectra (FTIR) of TE–IN samples

通過變溫紅外（VT-IR）、動(dòng)態(tài)熱機(jī)械分析（DMA）及應(yīng)力松弛行為驗(yàn)證了彈性體優(yōu)異的動(dòng)態(tài)可逆性（圖3）。通過彈性體中離子鍵的動(dòng)態(tài)解離和重組，可將有機(jī)硅彈性體的斷裂面有效修復(fù)，修復(fù)效率可達(dá)97%以上，且多次修復(fù)后，修復(fù)效率仍可達(dá)92%以上（圖4和圖5）。此外，制備的雙交聯(lián)有機(jī)硅彈性體具有優(yōu)異的回收性能，回收后彈性體拉伸強(qiáng)度可恢復(fù)90%以上，多次回收后拉伸強(qiáng)度仍可恢復(fù)85% 以上�；厥蘸髲椥泽w仍具有優(yōu)異的自修復(fù)性能，多次修復(fù)后修復(fù)效率仍可達(dá)90%以上（圖6）。

圖3 VT-IR spectra of TE–IN10, (a) peak shift as heated from 40 to 120 °C by 10 °C/min, (b) peak shift during cooled from 120 to 40 °C by 10 °C/min. Variation of storage modulus E′ under various temperatures as a function of time, (c) IN samples, (d) TE–IN10 samples. Normalized stress-relaxation curves, (g) TE–IN10 samples under different temperatures and (h) elastomers containing various ionic bonds at 60 °C, (c) Linear fitting of relaxation time (τ) versus temperature according to the Arrhenius' equation, (d) Stress relaxation activation energy (Ea) of samples with various ionic bonds.

圖4 Illustration of self-healing mechanism.

圖5 (a) Repeated macro-repairing of damaged TE–IN10 samples. Stress-strain curves of virgin and self-healed silicone elastomers, (b) epeatedly healed TE–IN10 samples, (c) TE–IN10, TE–IN20 and TE–IN30 samples healed at 100 °C for 12 h.

圖6 Photographs for the reprocessing of TE–IN10 samples. (b-c) Stress-strain curves of virgin and reprocessed silicone elastomers, (b) repeatedly reprocessed TE–IN10 samples from 80 meshes, (c) self-healing properties of repeated reprocessed TE–IN10 samples.

制備的雙交聯(lián)有機(jī)硅彈性體具有優(yōu)異的透明度。隨著離子網(wǎng)絡(luò)含量的增加，可見光透光率仍可達(dá)90%以上，多次高溫?zé)嵝迯?fù)及回收后，可見光透光率仍可高達(dá)85%以上（圖7）。彈性體具有優(yōu)異的抗水解性能，即使80 ℃熱水處理48h，彈性體的力學(xué)性能、E'和Tg均無明顯降低，此外，經(jīng)80 ℃熱水處理48h，彈性體試樣仍具有高達(dá)90 %以上的修復(fù)效率（圖7）。

圖7 Transmittance of (a) silicone elastomers containing various ionic bonds, (b) TE–IN10 samples with different healing times, (c) stress-strain curves and (d) storage modulus E' and tan δ of TE–IN10 samples after hydro-thermally treated.

有機(jī)硅彈性體配方通過Form 2桌面式SLA 3D打印機(jī)，可打印出表面光滑和輪廓清晰的彈性體實(shí)體（如“GDUT”校名縮寫，“齒輪”和“幸運(yùn)星”），且有機(jī)顏料加入后不會(huì)影響固化速率。此外，3D打印出彈性體實(shí)體具有優(yōu)異的自修復(fù)性能，多次修復(fù)后，自修復(fù)效率仍可達(dá)99%以上。表明3D打印層狀堆疊不影響離子網(wǎng)絡(luò)的分布及可逆解離—重組過程。

圖8 (a) Schematic of SLA-based 3D printing. (b) 3D printed various geometries from TE–IN10 formula with different pigments, “GDUT” with 1.0 wt% RP–355, “Toothed Gears” in turn with 0.05 wt% BP–825, 0.05 wt% RP–355, and 1.0 wt.% BP–825, “Ascendant” with 0.05 wt% RP–355. (c) Photographs of self-healing 3D printed “Ascendant”. (d) Stress-strain curves of repeatedly self-healed 3D printed samples after 100 °C for 12 h.

因此，通過巰基-烯快速光聚合及熱可逆離子交聯(lián)的光—熱雙交聯(lián)方式，成功地制備出優(yōu)異透明度及抗水解性能的自修復(fù)可回收3D打印有機(jī)硅彈性體。對(duì)長時(shí)間打印出的復(fù)雜結(jié)構(gòu)的彈性體功能件具有重要意義，節(jié)能環(huán)保，延長使用壽命、降低成本。為基于可逆動(dòng)態(tài)離子締合誘導(dǎo)的快速固化自修復(fù)有機(jī)硅材料提供一種可行的方案。

論文鏈接：https://doi.org/10.1016/j.cej.2020.124142

作者所在課題組的主研方向?yàn)楦叻肿庸饣瘜W(xué)，包括巰基-烯光點(diǎn)擊化學(xué)、3D打印彈性體、3D打印自修復(fù)材料和多功能光引發(fā)劑，相關(guān)成果發(fā)表在《Progress in Polymer Science》、《Journal of Materials Chemistry C》《Polymer Chemistry》《Langmuir》、《Journal of Photochemistry & Photobiology A: Chemistry》、《ChemPhotoChem》（Angewandte Chemie International Edition, Chemistry - ChemPhotoChem）和《Progress in Organic Coatings》等該領(lǐng)域TOP國際主流期刊上。

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