TY - JOUR
T1 - Quadruple hydrogen bond-containing a-ab-a triblock copolymers
T2 - Probing the influence of hydrogen bonding in the central block
AU - Liu, Boer
AU - Chen, Xi
AU - Spiering, Glenn A.
AU - Moore, Robert B.
AU - Long, Timothy E.
N1 - Funding Information:
Funding: This material is based in-part upon work supported by the National Science Foundation under grant no. DMR-1809291.
Funding Information:
Acknowledgments: The authors acknowledge Jae Sang Lee, Matthew D. Green, and Diana Convey for the expertise and instrumentation for AFM in Eyring Materials Center at Arizona State University. The authors thank the insightful discussion with Kailong Jin and Tyler B. White. The authors thank the support from Department of Chemistry and Macromolecules Innovation Institute (MII) at Virginia Tech, and School of Molecular Sciences and Biodesign Center for Sustainable Macromolecular Materials and Manufacturing (SM3) at Arizona State University.
Publisher Copyright:
© 2021 by the authors. Licensee MDPI, Basel, Switzerland.
PY - 2021/8/1
Y1 - 2021/8/1
N2 - This work reveals the influence of pendant hydrogen bonding strength and distribution on self-assembly and the resulting thermomechanical properties of A-AB-A triblock copolymers. Reversible addition-fragmentation chain transfer polymerization afforded a library of A-AB-A acrylic triblock copolymers, wherein the A unit contained cytosine acrylate (CyA) or post-functionalized ureido cytosine acrylate (UCyA) and the B unit consisted of n-butyl acrylate (nBA). Differential scanning calorimetry revealed two glass transition temperatures, suggesting microphase-separation in the A-AB-A triblock copolymers. Thermomechanical and morphological analysis revealed the effects of hydrogen bonding distribution and strength on the self-assembly and microphase-separated morphology. Dynamic mechanical analysis showed multiple tan delta (δ) transitions that correlated to chain relaxation and hydrogen bonding dissociation, further con-firming the microphase-separated structure. In addition, UCyA triblock copolymers possessed an extended modulus plateau versus temperature compared to the CyA analogs due to the stronger association of quadruple hydrogen bonding. CyA triblock copolymers exhibited a cylindrical microphase-separated morphology according to small-angle X-ray scattering. In contrast, UCyA triblock copolymers lacked long-range ordering due to hydrogen bonding induced phase mixing. The incorporation of UCyA into the soft central block resulted in improved tensile strength, extensibility, and toughness compared to the AB random copolymer and A-B-A triblock copolymer comparisons. This study provides insight into the structure-property relationships of A-AB-A supramolecular triblock copolymers that result from tunable association strengths.
AB - This work reveals the influence of pendant hydrogen bonding strength and distribution on self-assembly and the resulting thermomechanical properties of A-AB-A triblock copolymers. Reversible addition-fragmentation chain transfer polymerization afforded a library of A-AB-A acrylic triblock copolymers, wherein the A unit contained cytosine acrylate (CyA) or post-functionalized ureido cytosine acrylate (UCyA) and the B unit consisted of n-butyl acrylate (nBA). Differential scanning calorimetry revealed two glass transition temperatures, suggesting microphase-separation in the A-AB-A triblock copolymers. Thermomechanical and morphological analysis revealed the effects of hydrogen bonding distribution and strength on the self-assembly and microphase-separated morphology. Dynamic mechanical analysis showed multiple tan delta (δ) transitions that correlated to chain relaxation and hydrogen bonding dissociation, further con-firming the microphase-separated structure. In addition, UCyA triblock copolymers possessed an extended modulus plateau versus temperature compared to the CyA analogs due to the stronger association of quadruple hydrogen bonding. CyA triblock copolymers exhibited a cylindrical microphase-separated morphology according to small-angle X-ray scattering. In contrast, UCyA triblock copolymers lacked long-range ordering due to hydrogen bonding induced phase mixing. The incorporation of UCyA into the soft central block resulted in improved tensile strength, extensibility, and toughness compared to the AB random copolymer and A-B-A triblock copolymer comparisons. This study provides insight into the structure-property relationships of A-AB-A supramolecular triblock copolymers that result from tunable association strengths.
KW - Acrylic thermoplastic elastomer
KW - Microphase separation
KW - Quadruple hydrogen bonding
KW - Supramolecular polymer
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U2 - 10.3390/molecules26154705
DO - 10.3390/molecules26154705
M3 - Article
C2 - 34361857
AN - SCOPUS:85112086503
SN - 1420-3049
VL - 26
JO - Molecules
JF - Molecules
IS - 15
M1 - 4705
ER -