RAFT Polymerization of Styrene and Maleimide in the Presence of Fluoroalcohol: Hydrogen Bonding Effects with Classical Alternating Copolymerization as Reference

Abstract

Abstract:The impacts of hydrogen bonding on polymerization behavior has been of interest for a long time; however, universality and in-depth understanding are still lacking. For the first time, the effect of hydrogen bonding on the classical alternating-type copolymerization of styrene and maleimide was explored. N-phenylmaleimide (N-PMI)/styrene was chosen as a model monomer pair in the presence of hydrogen bonding donor solvent 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP), which interacted with N-PMI via hydrogen bonding. Reversible addition-fragmentation chain transfer polymerization (RAFT) technique was used to guarantee the "living" polymerization and thus the homogeneity of chain compositions. In comparison with the polymerization in non-hydrogen bonding donor solvent (toluene), the copolymerization in HFIP exhibited a high rate and a slight deviation from alternating copolymerization tendency. The reactivity ratios of N-PMI and St were revealed to be 0.078 and 0.068, respectively, while the reactivity ratios in toluene were 0.026 and 0.050. These interesting results were reasonably explained by using computer simulations, wherein the steric repulsion and electron induction by the hydrogen bonding between HFIP and N-PMI were revealed. This work first elucidated the hydrogen bonding interaction in the classical alternating-type copolymerization, which will enrich the research on hydrogen bonding-induced polymerizations.

Patterning Polyelectrolyte Complexes with Alternating Monomer Sequence Distributions

“…Carbon NMR confirmed that the maleimide content of purified products was less than 50%, so 2D HSQC and TOCSY NMR experiments were employed to examine the alternating tendency (see Supporting Information). While previous studies have investigated alternating tendency through studies of reactivity ratios, 24,32 MALDI-TOFS, 33 or through NMR chemical shifts of the backboneadjacent styrene carbon, 34 we used 2D NMR to avoid conflation of monomer sequence peaks with those of the strongly polarizing trimethyl ammonium group adorning the aromatic ring. Maleimide methine protons were found to correlate strongly with the styrenic methylene and methine protons, confirming the presence of alternating sequences along the polymer backbone.…”

“…The complexation of oppositely-charged homopolyelectrolytes is known to result in solid precipitates or liquid coacervates. 22,24,35,36 In this phase separation process, the intricate balance of electrostatic forces and other non-covalent interactions dictates the nature of the resultant bulk complex product. The density, strength, and arrangement of associating groups are particularly important to controlling the dynamics and underlying physics.…”

“…20,21 Pfeifer and Lutz first demonstrated the viability of installing distinct maleimides over time during the controlled propagation of polystyrene via atom transfer radical polymerization, 22 which can afford sequence specific polymers via its chain growth writing mechanism. 23 At the molecular level, alternating styrene/maleimide systems have increased chain stiffness 24 and can be easily modified to link pendant groups to the main chain for nonlinear optics, 25,26 supramolecular materials, 27 fluorimetric sensing 28 or polymer electrolytes. 29 However, to the extent of our knowledge, there are no examples to date of bringing this strategy to synthetic designer polyelectrolytes to modulate the physical state of polyelectrolyte complexation.…”

Patterning Polyelectrolyte Complexes with Alternating Monomer Sequence Distributions

“…20,21 Pfeifer and Lutz first demonstrated the viability of installing distinct maleimides over time during the controlled propagation of polystyrene via atom transfer radical polymerization, 22 which can afford sequence specific polymers via its chain growth writing mechanism. 23 At the molecular level, alternating styrene/maleimide systems have increased chain stiffness 24 and can be easily modified to link pendant groups to the main chain for nonlinear optics, 25,26 supramolecular materials, 27 fluorimetric sensing 28 or polymer electrolytes. 29 However, to the extent of our knowledge, there are no examples to date of bringing this strategy to synthetic designer polyelectrolytes to modulate the physical state of polyelectrolyte complexation.…”

Trends in Polymers 2017/2018: Polymer Synthesis

“…-hexafluoro-2-propanol (HFIP) was investigated by Zhu and coworkers [20]. In comparison to the toluene (reactivity ratio PMI 0.078, styrene 0.068), considerably different copolymerization parameters were observed in HFIP (reactivity ratio PMI 0.026, styrene 0.050), i.e., a less alternating tendency of the copolymerization was observed.…”