Order−Disorder Transition in Comblike Block Copolymers Obtained by Hydrogen Bonding between Homopolymers and End-Functionalized Oligomers: Poly(4-vinylpyridine)−Pentadecylphenol

Dynamic mechanical spectroscopy (DMS) is used to further investigate the recently observed order−disorder transition (ODT) in comblike block copolymers obtained by hydrogen bonding between poly(4-vinylpyridine) and pentadecylphenol (P4VP−PDP x ). For stoichiometric amounts of pyridine and phenol, i.e., x = 1.0, the ODT to a lamellar structure occurs at T ≃ 65 °C. The dynamic moduli G ‘ and G ‘‘ simultaneously show a crossover from a liquidlike behavior ( G ‘ ∼ ω 1.5 and G ‘‘ ∼ ω) to a response intermediate between a Newtonian fluid and a solid ( G ‘ ≈ G ‘‘ ∼ ω 1/2 ). The behavior above T ODT differs slightly from a homopolymer melt ( G ‘ ∼ ω 2.0 ) due to composition fluctuations, whereas the behavior below T ODT is characteristic for quenched block copolymer lamellar phases with local uniaxial order and global isotropy. Near room temperature, a transition to solid behavior ( G ∼ ω 0 ) takes place due to crystallization of the alkyl side chains. Larger amounts of PDP lower the T ODT temperature, and for x = 2.0 the transition to solid response occurs directly from the disordered state. Small and wide angle X-ray scattering (SAXS and WAXS) experiments and differential scanning calorimetry (DSC) corroborate these findings. Furthermore, SAXS and WAXS demonstrate that the low-temperature state of P4VP−PDP 2.0 is not stable and indicate that ultimately macrophase separation into a pure crystalline PDP phase and a microphase separated P4VP−PDP phase occurs.