DEVELOPMENT OF BIPHENYL MONOMERS AND ASSOCIATED CROSSLINKED POLYMERS WITH INTRAMOLECULAR PI-PI INTERACTIONS

Area of Science:

• Polymer Chemistry
• Materials Science
• Organic Chemistry

Background:

• Biphenyl moieties are incorporated into polymer networks to introduce specific properties.
• Covalently crosslinked polymers can exhibit complex network behaviors beyond simple covalent bonds.

Purpose of the Study:

• To synthesize and characterize novel polymers containing biphenyl units.
• To investigate the relationship between crosslinking density and network properties (swelling, mechanical modulus).
• To explore the influence of noncovalent interactions within the polymer network.

Main Methods:

• Synthesis of acrylated biphenyl monomers: 2-phenylphenolmonoacrylate (2PPMA), 4-phenylphenolmonoacrylate (4PPMA), and 4,4'-dihydroxybiphenyldiacrylate (44BDA).
• Characterization of monomers and polymers using differential scanning calorimetry (DSC), nuclear magnetic resonance (NMR), and Fourier transform infrared spectroscopy (FTIR).
• Polymerization via free radical reactions and evaluation of network properties through swelling studies and compressive modulus tests.

Main Results:

• Successful synthesis and characterization of biphenyl-containing monomers and polymers.
• Compressive modulus increased with higher crosslinker content, as expected.
• Swelling studies showed an unexpected trend, with swelling ratio not decreasing as crosslinker content increased.

Conclusions:

• The synthesized polymers exhibit both covalent crosslinks and noncovalent interactions.
• Intramolecular interactions between biphenyl side groups are hypothesized to cause the unexpected swelling behavior, acting as noncovalent crosslinks.
• The study highlights the importance of considering noncovalent interactions in designing polymer networks.