Structural Study of Four-Armed Amphiphilic Star-Block Copolymers: Pristine and End-Linked Tetronic T1307

详细信息    查看全文

• 作者：Kell Mortensen ; Masahiko Annaka
• 刊名：ACS Macro Letters
• 出版年：2016
• 出版时间：February 16, 2016
• 年：2016
• 卷：5
• 期：2
• 页码：224-228
• 全文大小：319K
• ISSN：2161-1653

文摘

We present a comparative structural study of 30 wt % aqueous suspensions of two related systems based on 4-arm PEO–PPO type of macromolecules (Tetronic T1307, BASF) with the PPO block near the star center. One system concerns the pristine 4-arm PEO–PPO star block copolymer T1307. The second system is a 1:1 blend consisting of, respectively, tetra-amine (TAT) and tetra-N-hydroxysuccinimide (TNT) terminated T1307. The two systems show common characteristics which are also known from linear PEO–PPO type of copolymers (Pluronic, BASF): at low temperatures the measured structure is dominated by the characteristics of individual molecules, while at higher temperatures hydrophobic effects of the PPO domains cause self-assembly into spherical or rodlike micelles. These micelles form in both systems ordered mesophases. The pristine T1307 copolymer suspension behaves generally very similarly to linear PEO–PPO type of di- and triblock copolymers: unimers at low temperatures associating into micelles at higher temperatures, forming subsequently cubic and hexagonal phases upon further increase in temperatures. The cubic phase of the 30 wt % Tetronic T1307 has FCC symmetry. The structure of the cross-linked 30 wt % 1:1 TAT–TNT system is basically organized into two-dimensional network sheets. At low temperatures the system is rather disordered but still with a sharp correlation peak which is associated with the distance between neighboring network sheets. Upon raising temperatures, PPO self-assembly causes organization across neighboring sheets, resulting in cylinder-like assemblies perpendicular to the sheets. These cylinders form hexagonal structure.