Mechanisms of molecular interactions in polybase–polyacid complex formed by copolymers of N,N‐dimethylaminoethylmethacrylate with alkylmethacrylates and methacrylic acid with ethylacrylate

Abstract

Mechanisms of molecular interaction in the blends of a polybase, a copolymer of N,N-dimethylaminoethylmethacrylate with methylmethacrylate and butylmethacrylate (PDMAEMA-MMA/BMA), with a polyacid, a copolymer of methacrylic acid with ethylacrylate (PMAA-co-EA), and plasticizer, triethylcitrate (TEC), have been investigated with FTIR Spectroscopy and potentiometry. To evaluate the strengths of hydrogen and ionic bonds in the polyelectrolyte complexes, quantum-chemical calculations were performed. According to this analysis, the energy of ionic and hydrogen bonding diminishes in the order: multi-component complexes involving protonated aminogroup of DMAEMA (ammonium cation) in the presence of chlorine counterion with ionized or unchanged carboxyl groups and water molecules (690-520 kJ/mol) > ternary H-bonded acid-base complexes associated with molecule of water (520-420 kJ/mol) > binary ionic complex of carboxylate anion and ammonium cation (404 kJ/ mol) > H-bonded complex of carboxylate and ammonium ions (257 kJ/mol) > binary H-bonded complex of uncharged carboxyl group with ammonium cation (114 kJ/mol) > ternary H-bonded complex of uncharged carboxyl group, aminogroup and water molecule (43 kJ/mol) > binary H-bonded complex between nonionized carboxyl and amino groups (26 kJ/mol). Proton-donating capability of functional groups in the studied polyelectrolyte blends diminishes in the order: HN þ (CH 3 ) 2 À > HOOCA > HOA. The proton-donating capacity can be significantly improved in the presence of Cl À ions, the effect of which may be appreciably inhibited if Na þ cations are available in the blend or solution. Proton-accepting capability weakens in the order: uncharged aminogroup > carboxylate anion > uncharged carboxyl group > hydroxyl group. The results of quantum chemical calculations facilitate interpretation of FTIR spectra.

Pressure sensitive adhesives based on interpolymer complexes

“…At this pH the amino-terminated surfaces can be considered to be protonated and to carry strong positive surface charges. As pH increases above [336] and adhesion increases. A similar adhesion force profile between an aminoterminated AFM tip and an amino-terminated flat surface was reported by Vezenov et al [337].…”

“…In addition to the non-compensated strong van der Waals forces within the contact area, ammonium groups of protonated amino-terminated polymer form strong hydrogen bonds with OH groups on the surface of silica substrate [336]. Such hydrogen bonds become especially strong in the presence of chloride counterions, as has been shown in [336]. As a result of such strong interfacial hydrogen bonding, a maximum adhesion force was measured.…”

“…The Clcounterion effect may be appreciably inhibited if Na + cations are present in the solution. Protonaccepting capability weakens in the order: Uncharged aminogroup > Carboxylate anion > Uncharged carboxyl group > Hydroxyl group [336].…”

“…The reduced protonation translates into a reduced positive surface charge density on the probe particle, diminishing the attractive H-bond contribution which, and, in turn, leads to a decrease in adhesion forces. At higher pH, above 10, the amino-terminated probe contains no proton-donating ammonium groups, while silica surface is covered by hydroxyl groups, which capable of forming very weak hydrogen bonds with nonprotonated amino groups [336], resulting in a decrease of adhesion asymptotically approaching zero.…”

“…In the PSAs based on polyelectrolyte complexes, the same polymer component may be According to the quantum analysis of more than 300 polyelectrolyte complex structures examined in [336] (see Table 9), the ionic complexes formed with the participation of charged polyelectrolyte functional groups (ammonium cation and carboxylate anion) are from 4 to 16 times more energetically favorable than the strongest H-bonded complexes of uncharged complementary polybase and polyacid groups [336]. These energies control both the phase state and the cohesive strength of the PSAs based on the polyelectrolyte complexes.…”