Rheology of hydrogen-bonded dendritic supramolecular polymer networks in the melt state

- Melt rheological properties of H-bonded dendritic polymer networks are studied.
- The association of different polymers is driven by complementary Ba/HW interactions.
- The formation of H-bonded networks is proven by the observation of a rubbery plateau.
- The association of the supramolecular polymers is extremely temperature sensitive.
- Besides the H-bonded aggregation, additional polymer phase segregation is proposed.

We investigate the rheological properties of a series of complex supramolecular dendritic polymer networks in the melt state, which are generated by the association between tri-barbiturate (Ba) functionalized poly(n-butyl acrylate) (PnBuA), (Ba-(PnBuA-Ba)2), and several bis-Hamilton wedge (HW) functionalized polymers, including a semifluorinated copolymer HW-P(nBuA-co-PFPA)-HW, (PFPA, 2,2,3,3,3-pentafluoropropyl acrylate); a semifluorinated homopolymer HW-PPFPA-HW and two nonfluorinated homopolymers HW-PnBuA-HW and HW-PI-HW (PI, polyisoprene). The association of the different polymers leads to dendritic phase segregated structures, held together solely by specific H-bonding moieties in the sense of a key/lock system. It is known that frequency-dependent rheology is suited to exploit the time- and temperature-dependent association of supramolecular polymers in the melt state. Moreover, any change of the polymer backbone related to a change of its polarity and glass transition temperature (Tg) will lead to a strong effect on the thermo-rheological properties. For the stoichiometric mixture of Ba-(PnBuA-Ba)2 with its linear complementary partners, such as HW-PnBuA-HW, HW-P(nBuA-co-PFPA)-HW, and HW-PPFPA-HW rubbery materials have been observed in all cases, each of them revealing a pronounced rubbery plateau in frequency-dependent rheology measurements from 0 to 50 °C driven by hydrogen-bonding (H-bonding) association. Distinct network effective strands (νe) and supramolecular bond lifetimes (τ) have been determined by rheology measurements. Moreover, as the small angle X-ray scattering (SAXS) profiles do not indicate the formation of supramolecular clusters or disordered micelles in the melt state, the formation of homogeneous, dendritic supramolecular networks has been proposed.

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