Order−Disorder Transition in Comblike Block Copolymers Obtained by Hydrogen Bonding between Homopolymers and End-Functionalized Oligomers: Poly(4-vinylpyridine)−Pentadecylphenol
Tutkimustuotos: Lehtiartikkeli › › vertaisarvioitu
- University of Helsinki
- Daresbury Laboratory
- University of Groningen
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-PDPx). 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′ ∼ ω1.5 and G″ ∼ ω) to a response intermediate between a Newtonian fluid and a solid (G′ ≈ G″ ω1/2). The behavior above TODT differs slightly from a homopolymer melt (G′ ∼ ω2.0) due to composition fluctuations, whereas the behavior below TODT is characteristic for quenched block copolymer lamellar phases with local uniaxial order and global isotropy. Near room temperature, a transition to solid behavior (G ∼ ω0) takes place due to crystallization of the alkyl side chains. Larger amounts of PDP lower the TODT 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 calonmetry (DSC) corroborate these findings. Furthermore. SAXS and WAXS demonstrate that the low-temperature state of P4VP-PDP2.0 is not stable and indicate that ultimately macrophase separation into a pure crystalline PDP phase and a microphase separated P4VP-PDP phase occurs.
|Tila||Julkaistu - 1997|
|OKM-julkaisutyyppi||A1 Julkaistu artikkeli, soviteltu|