Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/3442
標題: Crystallization-induced orientation for microstructures of PS-PLLA
結晶誘導定位PS-PLLA團聯共聚合物奈米微結構之探討
作者: TSENG, WEN-HSIEN
曾文賢
關鍵字: block copolymer;團聯共聚合物;crystallization induced;結晶誘導
出版社: 化學工程學系
摘要: 
本實驗利用活性自由基聚合反應(living free radical polymerization)與活性開環聚合反應(living ring opening polymerization),製備可結晶性(crystallizable)聚苯乙烯聚左旋乳酸雙團聯共聚合物(polystyrene-b-poly(L-lactide), PS-PLLA)。相對於PS-PLLA在非晶相之基材上呈現無序之層板微結構,以一具晶格吻合性之結晶性基材Benzoic acid(BA)與另一不具晶格吻合性之結晶性基材hexamethylbenzene (HMB)誘導PS-PLLA皆形成大範圍定向之奈米微結構。分析實驗結果判斷結晶誘導定向PS-PLLA微結構之機制為PS-PLLA之微觀相分離過程與結晶基材以共晶(eutectic)形式直接形成。且經由穿透式電子顯微鏡(transmission electron microscopy)之形態觀察顯示,結晶性基材結晶後即能誘導非晶相之PS-PLLA形成大範圍定向之有序結構。並根據實驗之結果顯示,大範圍定向結構之形成與晶格之吻合性、結晶鏈段結晶與否無關;主要決定步驟為PS-PLLA與結晶基材形成之共晶形態於基材結晶時,直接固化(solidification)之效應誘導PS-PLLA微觀相分離形態形成大範圍定向之奈米微結構。根據實驗之結果並結合文獻所報導之假設性相圖與形成模型[26],本實驗也成功地建立符合PS-PLLA雙團聯共聚合物系統之相圖(phase diagram),與結晶誘導大範圍定向奈米微結構機制之形成模型。
同時本實驗亦利用穿透式電子顯微鏡(transmission electron microscopy, TEM)之形態觀察與電子繞射圖譜(electron diffraction pattern, ED)之繞射模式分析此特殊結晶誘導機制下之結晶結構,有趣的是不同於一般文獻針對均聚合物或是高分子團聯共聚合物所形成之結晶分子鏈構形,經由結晶誘導後之薄膜形態,其結晶分子鏈為平行於基板方向排列之形態(edge-on),本實驗之材料PS-PLLA系統經由結晶誘導後所形成之結晶分子鏈構形對應基材呈現垂直之形態(flat-on)。
本研究也將針對結晶誘導形成大範圍且有序之奈米微結構薄膜,進一步利用水解(hydrolytic degradation)的方式,製備奈米成形模板(nanopatterned template)。將對於不同物種之團聯鏈段作高選擇性的腐蝕; 若採用水解的方式,則可利用NaOH(0.5M)水溶液及NaOH(0.5M) :CH3OH =3:2(v/v)的溶液對PLLA部分進行劣解。換言之,利用分解腐蝕的選擇性,因而可有效的製備出具有蝕刻效果之奈米成形模板。

Semi-crystalline diblock copolymers, poly(styrene)-b-poly (L-lactide) (PS-PLLA), have been synthesized by living free radical and ring opening polymerization in sequence. The formation of large-sized, well-oriented phase-separated microdomains of PS-PLLA was successfully achieved by using different crystalline substrates such as benzoic acid (BA) and hexamethylbenzene (HMB) whereas disorder lamellar texture was obtained on amorphous substrates. Crystallization-induced orientation of PS-PLLA microstructure is attributed to directional crystallization of eutectic type between microphase- separated PS-PLLA and crystalline substrate. As evidenced by transmission electron microscopy (TEM) observations, well- oriented PS-PLLA lamellar morphology forms after the crystallization of substrates, regardless of the crystallization of block copolymers. Furthermore, defects of the interface in HMB crystalline substrate are much more than in BA crystalline substrate in according to morphological observation of TEM. As the mention above, lattice matching is not a decisive factor to determine the crystallization-induced orientation for crystallizable block copolymers.
Surprisingly, a flat-on crystalline morphology (i.e., with the chain axis normal to the substrate) was obtained, as evidenced by single-crystal-like [001] zonal electron diffraction (ED). By contrast, an edge-on crystalline morphology (i.e., with the chain axis parallel to the substrate) was observed for PLLA homopolymer under the same condition. The crystallographic organization of PLLA-PS microdomains as observed by transmission electron microscopy, ED suggests that the growth direction of PLLA crystals is along a axis direction that suggests that the growth direction of PLLA crystals is along a axis direction that corresponds well with the preferential growth direction (i.e., b axis direction) of BA or HMB crystals. As a result, the phase-separated lamellar morphology consists of an alternation of flat-on layer of PLLA lamellae and of amorphous layer of PS components.
Hydrolytic degradation of PS-PLLA was used to create nanopatterned templates from crystallization-induced monodomain of thin film samples. Block copolymers consist of distinct components (e.g., PS or PLLA) could be selectively degraded by hydrolytic degradation. Solution of NaOH (0.5M) or NaOH (0.5M):CH3OH = 3:2(v/v) solution can be used to degrade the crystalline and amorphous PLLA domains. Owing to the high selectivity of degradation, nanopatterned template can be successfully prepared from the biodegradable thin-film samples.
URI: http://hdl.handle.net/11455/3442
Appears in Collections:化學工程學系所

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