Molecular dynamics and morphology in the blends of a network-forming reactive polymer and an amphiphilic block copolymer were examined as a function of the advancement of chemical reactions. In the blends containing a triblock copolymer, both microscopic (domains of the order of micrometers) and nanoscopic (domains of the order of nanometers) phase separations were observed during network formation. Interestingly, only nanoscopic phase separation was found in the blends containing a diblock copolymer. The shape and the origin of these nanoscopic features were investigated by atomic force microscopy and were found to be a function of blend composition. A concept was advanced of the three-phase nanostructured morphology that begins to form with self-assembly of one block and continues to develop during network formation in the postassembly stage. The changes in relaxation dynamics that accompany network formation were monitored by broad-band dielectric relaxation spectroscopy (DRS) and were shown to represent a signature of the morphological state of the blend. The ability of DRS to identify and deconvolute various relaxation processes during network formation and phase separation is noteworthy and should be exploited as means of monitoring and controlling the development of nanostructured morphology in these complex systems.

The reorientational dynamics of dipoles in poly(vinylidene fluoride)/poly(methyl methacrylate) (PVDF/PMMA) blends were investigated by dielectric spectroscopy. Measurements were performed over a wide range of temperature and frequency, and previously unavailable results are reported. Various relaxation processes were identified and their locations assigned to the different morphological regions in PVDF, PMMA, and PVDF/PMMA blends. The development of a relaxation process associated with the imperfections in the crystalline phase was recorded both in pure PVDF and in crystalline blends. An amorphous interphase and a liquid-like amorphous phase are present in pure PVDF, but their relaxation dynamics are dielectrically indistinguishable, giving rise to a single non-Arrhenius relaxation mechanism. In the crystalline blends, however, the interphase is devoid of PMMA, and its relaxation dynamics are readily distinguishable from those of the PVDF/PMMA miscible phase. Interestingly, the relaxation dynamics in the interphase were found to vary as a function of blend composition. Since the relaxation processes are governed by cooperativity, an explanation of our findings is offered in terms of the interactive nature of the relaxation process.

An investigation was carried out of the molecular dynamics of poly(l-lactic acid) before, during, and after crystallization. Experimental results were generated over a wide range of temperature and frequency by broad-band dielectric relaxation spectroscopy (DRS). An interesting finding is that the average relaxation time (defined as τ = 1/2πf max, where f max is the frequency at maximum loss for the α process) does not vary with degree of crystallinity during melt and/or cold crystallization. Moreover, the temperature dependence of the average relaxation time for wholly amorphous and crystallized samples is well-described by a single Vogel−Fulcher−Tammann (VFT) functional form. The unchanged fragility suggests that the segmental dynamics are not sensitive to the different degree of crystallinity, implying that the relaxing segments are smaller than the thickness of the amorphous layers between lamellae. Apparently, the distance between lamellae is greater than the length of the primitive segment and the characteristic size of the cooperatively rearranging domain; the length scale of the α process is thence put at less than 4 nm.

A comprehensive investigation of the reorientational dynamics of poly(vinylidene fluoride)/ poly(methyl methacrylate) (PVDF/PMMA) blends was carried out. Dielectric relaxation spectroscopy (DRS) was performed over 11 decades of frequency and over a wide range of temperature on wholly amorphous, crystalline, and crystallizing blends of varying composition. The range of experimental conditions and compositional variables far exceeded those employed by previous investigators, enabling us to formulate a comprehensive view of the dynamics in these systems. A number of relaxation processes were detected, and their origins, temperature dependence, composition dependence, and spectral characteristics were established. Three R-type processes were observed: the R a process, associated with relaxations of all amorphous PVDF segments (not only within the crystalline-amorphous interphase); the Rm process, which encompasses several relaxation processes and scales with blend composition; and the Rc process, attributed to relaxations within the crystalline phase. With decreasing temperature the Ra process in the blends undergoes a crossover to a localized βa process, in a manner different from the Rβ splitting observed in many molecular and polymeric glass formers. An explanation of the underlying physics was offered within the framework of an interplay between the physical dimension of various nanoscopic regions in the blend and the characteristic length scale for cooperative relaxation. The Raβa crossover was shown to be a consequence of the confinement imposed on the amorphous PVDF segments by more rigid PMMA segments and the PVDF crystals.

A liquid crystal monomer (LCM) was synthesized and attached as a side chain to a siloxane polymer (SCLCP). The molecular dynamics of LCM and SCLCP were investigated by broad-band dielectric relaxation spectroscopy (DRS) over 10 decades of frequency. The surface treatment of the electrodes was found to have a pronounced effect on the macroscopic alignment and dynamics. In the isotropic state the relaxations in LCM and SCLCP are well-described by the Kohlrausch-Williams-Watts (KWW) functional form. In the LC state, the overall dielectric response is a weighted sum of two dispersions that depend on the macroscopic alignment. The hometropic (H) alignment is dominated by the (slower) δ process, while the planar (P) alignment is dominated by the (faster) R m process. Both processes are symmetric and can be described by Cole-Cole (CC) or Fuoss-Kirkwood (FK) functional forms. The δ process governs the dynamics in the SCLCP near the glass transition, similar to the segmental R process in non-LC glass formers. Excellent agreement was observed with the various aspects of the seminal work by Attard and Williams.