Microphase Separation Transformation in Bio-Based Benzoxazine/Phenolic/PEO-<i>b</i>-PCL Diblock Copolymer Mixtures Induced by Transesterification Reaction
Yang‐Chin Kao, Yi-Cheng Ku, Mohamed Gamal Mohamed, Wei‐Hung Su, Shiao‐Wei Kuo
Abstract
High Resolution Image Download MS PowerPoint Slide Herein, we synthesized a difunctionalized bio-based vanillin azine monomer (4,4′-((1 E,1′ E )-hydrazine-1,2-diylidenebis(methaneylylidene))bis(2-methoxyphenol), VBAZ-2OH) via a Schiff base reaction between vanillin and hydrazine monohydride. Subsequently, we successfully prepared 2,2′-(((1 E,1′ E )-hydrazine-1,2-diylidenebis(methaneylylidene))bis(8-methoxy-2 H -benzo[ e ][1,3]oxazine-6,3(4 H )-diyl))bis(ethan-1-ol), VBAZ-BZ-2OH), which contains oxazine units, through a Mannich condensation reaction of VBAZ-2OH with ethanolamine and paraformaldehyde in 1,4-dioxane as the solvent. The chemical structures of these two monomers (VBAZ-2OH and VBAZ-BZ-2OH) were characterized by using NMR and FTIR analyses. Our study aimed to investigate the transesterification reactions by blending different VBAZ-BZ-2OH/phenolic resin (BP) compositions with a PEO 112 - b -PCL 99 (EC) diblock copolymer to form various BP/EC blends. These blends exhibit competitive hydrogen-bonding interaction phenomena, which were analyzed using one-dimensional and two-dimensional FTIR analyses. Interestingly, after thermal treatment of BP/EC blends at 150 °C, the ordered self-assembled lamellae or hexagonal packed cylinder structures transform into the disordered micelle or disorder structure in BP/EC blends as a result of the transesterification reaction due to EC becoming miscible with a VBAZ-BZ-2OH monomer, disrupting the ordered self-assembled structure, which was confirmed through TEM and SAXS analyses. The transesterification reaction could easily understand the order–disorder morphological transformation using BP/EC blends to replace thermogravimetric analysis (TGA) coupled with microcomputed gas chromatography (TGA-GC) analyses.