The crystallization and dynamics of hyperbranched poly(ethylene oxide) (hbPEO), obtained from the direct random copolymerization of EO and glycidol (PEO-co-PG), are studied both in bulk and within nanoporous alumina (AAO). Copolymerization decreases the degree of crystallinity and lowers the crystallization and melting temperatures as compared to linear PEO. The dynamics of capillary imbibition within AAO followed the t1/2 prediction but is slower than predicted by the classical Lucas–Washburn equation. The most prominent effect of confinement is the change in nucleation mechanism—from heterogeneous nucleation in bulk to homogeneous nucleation inside AAO. The homogeneous nucleation temperatures for the hyperbranched PEOs agree with those of linear ones provided that the branch molecular weight is used instead of the total molecular weight. Confinement and interfacial effects further suppress the degree of crystallinity and speed up the segmental dynamics.

Polymethacrylates with polyhedral oligomeric silsesquioxane (POSS) moieties (poly(POSS-MA)s) with flexible spacers between the POSS cages and the methacrylate group have distinctly different properties from their linear counterpart, i.e., PMMA. POSS cages modify interchain correlations and result in multiple dynamic processes that reflect the cooperative relaxations of both the pendant POSS units and ester dipoles and the polymer backbone. As a result, the freezing of the backbone dynamics is shifted to lower temperatures, and the nanocomposites appear softer than linear PMMA chains of similar degrees of polymerization. POSS cages can be employed as nanometer size blocks that, depending on the polymer backbone and the spacer, can impart mobility and control over the mechanical properties of nanocomposites.

Diblock copolymers of poly(isoprene-b-ethylene oxide), PI-b-PEO (IEO), are employed as templates for the development of nanostructured polymer electrolytes by salt-doping. For this purpose, lithium triflate (CF3SO3Li, LiTf) and 1-ethyl-3-methylimidazolium trifluoromethanesulfonate (CF3SO3–C6H11N2, EMITf) salts were separately introduced at various [EO]:[salt] ratios. The local structure, nanodomain morphology and ion dynamics of the resulted block copolymer electrolytes were investigated by infrared spectroscopy, X-ray scattering, differential scanning calorimetry and dielectric spectroscopy. The structural investigation revealed strong effects of both LiTf and EMITf salt addition to the copolymer nanodomain morphology. These include transitions between different ordered nanophases and an increased domain spacing. The latter was independent of the kind of salt providing the possibility of studying ion transport under identical nanodomain sizes but in the presence of different interactions. Ionic conductivity in the two systems was fundamentally different. In IEO/EMITf ionic conductivity was much higher and comparable to the PEO/EMITf case. However, in IEO/LiTf, ion conductivity was reduced by a factor of a 100 relative to the PEO/LiTf case. This reflects combined effects of increased interaction parameter and of preferential wetting of electrodes. These results suggest ways for manipulating ion transport in polymer electrolytes.

Diblock copolymers of poly(styrene-b-ethylene oxide), PS-b-PEO, are employed together with lithium triflate (CF3SO3Li, LiTf) at several [EO]:[Li] ratios as solid polymer electrolytes. Their thermodynamic state, self-assembly, and viscoelastic properties are discussed in conjunction with the ionic conductivity. PS-b-PEO/LiTf differs from the well-investigated PS-b-PEO/LiTFSI system in that the electrolyte in the former binds intramolecularly to PEO chains. Microscopic and macroscopic parameters affecting ion transport are discussed. From a microscopic point of view different parameters were considered as potential regulators of ion transport: the characteristic domain spacing, d, the interfacial thickness, Δ, and the ratio of Δ/d. By comparing two block copolymer electrolytes (PS-b-PEO and PI-b-PEO) bearing the same conducting block (PEO) and the same electrolyte (LiTf) but in the presence of different interactions, among the microscopic parameters it is the domain spacing that appears to have the most decisive role in ionic conductivity. Ion conductivity in PS-b-PEO/LiTf exhibits a molecular weight dependence similar to that reported for the PS-b-PEO/LiTFSI system, however, with somewhat lower values reflecting anion size effects. Among the macroscopic factors that limit ionic conductivity, the possible preferential wetting of the electrodes by either of the constituent phases can lead to an orientation that effectively blocks ion transport. The viscoelastic properties of the block copolymer electrolytes differ substantially from the neat block copolymers. Li-ion coordination affects not only the PEO segments but also, surprisingly, the PS segments. An increase in PS glass temperature by ∼10 K is reported. In addition, the viscoelastic properties suggest the formation of transient structures in the molten complex.

The Bjerrum length is approached in a low polarity solvent by encapsulating, both, a borate anion and a phosphonium cation in a rigid lipophilic dendrimer shell. In addition the cation size is varied by 34-fold. We thus obtain superweak ions with potential applications in catalytic processes.

The kinetics of crystallization (heterogeneous vs homogeneous nucleation) and the relation to the local segmental dynamics are studied in a series of poly(ethylene oxide)-b-poly(ε-caprolactone) (PEO-b-PCL) diblock copolymers confined within self-ordered nanoporous alumina (AAO) by X-ray scattering, polarizing optical microscopy, differential scanning calorimetry and dielectric spectroscopy. In the bulk and for the more asymmetric copolymer, the minority phase (PEO) nucleates solely via homogeneous nucleation. When the same diblock copolymers reside inside AAO, nucleation of PEO is completely suppressed. The majority block (PCL) is also affected by confinement and crystallizes at lower temperatures via homogeneous nucleation. These findings can be discussed in terms of the proposed temperature vs curvature “phase diagram”. In this diagram the melt and glassy states are separated by the two nucleation regimes, heterogeneous and homogeneous at high and low temperatures, respectively. Homogeneous nucleation is controlled by the faster part of the distribution of PCL segmental relaxation which under confinement speeds-up.

The dynamics of unentangled cis-1,4-polyisoprene confined within self-ordered nanoporous alumina (AAO) is studied as a function of molecular weight (5000–300 g/mol) and pore size (400–25 nm) with dielectric spectroscopy. The main effects are the pronounced broadening of both segmental and chain modes with decreasing AAO pore diameter. This suggests that the global chain relaxation is retarded on confinement. Remarkably, the distribution of relaxation times is broadened even within pores with size 50 times the unperturbed chain dimensions. The glass temperature is unaffected by confinement. These results are discussed in terms of confinement and adsorption effects. Confinement effects are negligible for the studied molecular weights. Chain adsorption, on the other hand, involves time and length scales distinctly different from the bulk that can account for the experimental findings.

The synthesis of a series of propeller-shaped hexaphenylbenzenes (HPB) substituted with one (3), two (1) and four (2) poly(ethylene glycol) (PEG) chains as well as of an ortho-connected trimer of HPBs bearing two PEG chains (4) result in remarkable amphiphiles with supramolecular organization and suppressed dynamics. The thermodynamic state and self-assembly are studied with DSC and X-ray diffraction whereas the dynamics of HPB core and PEG segments are elucidated via heteronuclear NMR and dielectric spectroscopy. The phase state is largely determined by the rod–coil nature and architecture of block copolymers comprising a HPB “mesogen’ and flexible PEG chains. In addition, the molecular shape of the ortho-connected trimer of HPBs (4) promotes π–π stacking and gives rise to a supramolecular columnar organization uncommon to most other HPBs. The emerging dynamic picture is that of practically frozen HPB cores that are surrounded by mobile PEG segments. The implications of this supramolecular organization—stacked/immobile HPB cores and flexible/fast moving PEG segments with suppressed crystallinity—to ion transport are discussed with respect to the conductivity measurements in amphiphiles doped with LiCF3SO3 salt at different [EG]:[Li+] ratios. A unique feature of the doped amphiphiles is the Vogel–Fulcher–Tammann temperature dependence of ionic conductivity with values that are comparable to the archetypal polymer electrolyte (PEG)xLiCF3SO3.

The thermodynamic, optical, structural, and dynamic properties of the semifluorinated (E)-1-(4-octylphenyl)-2-(4-(perfluorooctyl)phenyl)diazene (4) and the corresponding (E)-1,2-bis(4-octylphenyl)diazene (5) have been studied with differential scanning calorimetry, polarizing optical microscopy, X-ray diffraction, and dielectric spectroscopy. 4 combines the azobenzene properties with the fluorophobic effect and gives rise to a responsive material with a temperature and dc-bias-driven switchable dielectric permittivity within the narrower nematic phase. This is caused by the nematic potential that inevitably brings some fluorocarbon chains in proximity to the hydrocarbon chains from adjacent molecules. Frustration is alleviated by reducing the nematic-to-isotropic transition temperature and by increasing the crystalline-to-nematic transition temperature, thus limiting the stability of the nematic phase. Unlike the normal isotropic phase of compound 5, the isotropic phase of compound 4 contains dipoles with short-range orientation correlations. Optimizing the type of interactions may result in materials with applications as molecular switches and electrooptic devices.

Tethering amphiphiles symmetrically to a small benzene core – in analogy to semifluorinated alkanes (SFAs) – gives rise to self-assembly far more rich than any previously investigated SFA. The modulation of intermolecular interactions between hydrocarbon and fluorocarbon chains as well as additional π–π interactions of the cores are thought to be responsible for the rich self-assembly. The system is investigated with respect to thermodynamics, structure and dynamics, respectively, with differential scanning calorimetry, X-ray scattering and dielectric spectroscopy. The mechanical and nano-mechanical properties are studied with rheology and Brillouin light scattering covering a broad frequency range and spatial resolution. Starting from lower temperatures distinct phases are identified consisting of nanophase separated domains comprising crystalline or melted fluorocarbon/hydrocarbon domains. At intermediate temperatures lamellar phases are identified with molecular and supramolecular order. At higher temperatures domains composed of thermodynamically unfavorable yet kinetically mixed configurations exist. The latter phase is prone to annealing as these trapped configurations convert from locally segregated to more homogeneously mixed molecules. At higher temperatures a quasi-isotropic phase is formed composed of orientationally correlated dipoles.

The crystallization and local dynamics of poly(ε-caprolactone) (PCL) confined to self-ordered nanoporous alumina (AAO) were studied as a function of pore size, pore surface functionality, molecular weight and cooling/heating rate by differential scanning calorimetry (DSC), wide-angle X-ray diffraction and dielectric spectroscopy. In contrast to the bulk, PCL located inside nanoporous alumina crystallizes via several distinct nucleation mechanisms. All mechanisms display pronounced rate dependence. At low undercoolings, the usual heterogeneous nucleation of bulk PCL was suppressed at the expense of two additional mechanisms attributed to heterogeneous nucleation initiated at the pore walls. At higher undercoolings a broad peak was observed in DSC which we attribute to crystallization initiated by homogeneous nucleation. At high cooling rates, the critical nucleus size is smaller than the smallest diameter of pores. Thus, PCL is able to crystallize within the smallest pores, despite the lower degree of crystallinity. Inevitably, homogeneous nucleation is strongly coupled to the local viscosity and hence to the local segmental dynamics. Dielectric spectroscopy revealed that confinement affected both the rate of segmental motion with a lowering of the glass temperature as well as a broader distribution of relaxation times.

The crystallization of poly(ethylene oxide) (PEO) confined in self-ordered nanoporous alumina (AAO) containing aligned and straight cylindrical nanopores was studied as a function of molecular weight, pore size and cooling/heating rate by differential scanning calorimetry and X-ray scattering. Bulk PEO crystallizes via heterogeneous nucleation at defects and impurities whereas PEO confined to AAO crystallizes mainly via homogeneous nucleation. Molecular weight and cooling rate have a pronounced effect on the nucleation process. Dielectric spectroscopy revealed that confining PEO to AAO results in broadening of the distribution of relaxation times associated with the segmental α relaxation process and the secondary β process. Dielectric loss peaks become broader with decreasing pore diameter.

The phase state, local structure, local mobility, and viscoelastic response have been studied in the archetypal polymer electrolyte (PEO)xLiCF3SO3 with ether oxygen to lithium ion ratio of 2 ≤ [EO]/[Li] ≤12 over a broad temperature range in an effort to explore the factors controlling ionic conduction. We confirm that the crystal structure of the complex is identical to the (PEO)3LiCF3SO3 polymer electrolyte independent of the [EO]:[Li] content. Heating the nonstoichiometric compositions result in progressive melting of the complex, whereas the complex formed at or near the stoichiometric composition remains stable up to the liquidus temperature. The temperature dependence of dc conductivity is neither Arrhenius nor VFT. Its temperature dependence is more complex reflecting the underlying structural changes. Surprisingly, ionic conduction takes place both within the crystalline complex and in the amorphous phase with the latter having the major contribution. The (PEO)12LiCF3SO3 polymer electrolyte is the one with the highest conductivity at all temperatures investigated. The linear viscoelastic properties were studied as a function of temperature at two compositions. The different phases have distinct viscoelastic signatures. The complex formed at or near stoichiometric composition has a predominantly elastic response, whereas the more dilute compositions (consisting of the crystalline complex and an ion-containing amorphous phase) have a viscoelastic response and an ultraslow relaxation. Local polymer relaxation and ionic mobility are completely coupled. It is suggested that local ion jumps at subsegmental level are responsible for the measured conductivity.

Structure formation, phase behavior, and dynamics of mono-bromo hexa-peri-hexabenzocoronene (HBC-Br) are strongly affected by the confinement of cylindrical nanopores with rigid walls. Using self-ordered nanoporous anodic aluminum oxide (AAO)-containing arrays of aligned nanopores with narrow size distribution as a confining matrix, pronounced alignment of the HBC-Br columns along the nanopore axes was found to be independent of the pore diameter. Hence, arrays of one-dimensional supramolecular HBC-Br wires with the columns uniformly oriented along the wire axes on a macroscopic scale were obtained, unlike with discotics bearing smaller cores. The formation of the crystalline herringbone structure is shifted to lower temperatures in nanopores with diameters of a few hundred nanometers, whereas the formation of this low-temperature phase is completely suppressed when the pore diameter is below 20 lattice parameters. Moreover, the cylindrical confinement affects the disk axial dynamics as well as the distribution of relaxation times.Keywords: confinement; discotic liquid crystals; nanoporous aluminum oxide; supramolecular wires

The poly(vinyl acetate) (PVAc) segmental dynamics is studied as a function of composition, temperature, and pressure in thermodynamically miscible blends with poly(ethylene oxide) (PEO) by dielectric spectroscopy. In the PVAc-rich blends all short-range correlations are dominated by the PVAc component. An invariant frequency dispersion is found when the spectra at each blend composition are compared under isochronal conditions. The self-concentration model with a fixed PVAc self-concentration of ∼0.22 qualitatively describes the temperature dependence of the PVAc segmental dynamics both at atmospheric and at elevated pressures.

Biphasic fluorocarbon/hydrocarbon amphiphiles tethered to cores at distances commensurate with their packing requirement can provide thermodynamic pathways toward equilibrium. This contrasts with the analogous semifluorinated alkanes. The dynamics of a fluorous biphasic hexa(3,5-substituted-phenyl)benzene (HPB) is studied with dielectric spectroscopy as a function of temperature and pressure in comparison to the parent biphasic diphenylacetylene (DPA). Dielectric spectroscopy is a sensitive probe of the fluorocarbon environment through the end C–F dipole. Four dielectrically active processes were observed that associate with the CF3 environment within the different phases (isotropic, liquid-like lamellar, solid lamellar, glassy state). Pressure facilitates the construction of the equilibrium phase diagram. The kinetic pathways to fluorocarbon organization are explored by pressure-jump experiments. A highly cooperative process was found that is atypical of a nucleation and growth process expected for first-order transitions.

The crystallization of highly isotactic polypropylene confined in self-ordered nanoporous alumina is studied by differential scanning calorimetry. A transformation from a predominantly heterogeneous to predominantly homogeneous nucleation takes place if the pore diameter is smaller than 65 nm. Crystallization is suppressed with decreasing pore size, and the absence of nucleation below 20 nm pores indicates the critical nucleus size. The results reported here might enhance the understanding of nanocomposites containing semicrystalline polymers and reveal design criteria for polymeric nanofibers with tailored mechanical and optical properties.

The distinctly different unit cells, dipolar dynamics and viscoelastic properties of the two columnar phases in a dipole-functionalized discotic liquid crystal (mono-iodine hexa-peri-hexabenzocoronene) were employed as fingerprints and allowed investigating the kinetic pathways towards formation of the crystalline phase. X-Ray scattering, dielectric spectroscopy and rheology revealed a nucleation and growth process. The transformation involved coexisting unit cells composed from columns with either tilted or non-tilted disks and the absence of intermediate states. The transition can be described as a transformation from a structurally weakly ordered but dipolar well-ordered liquid crystalline phase to a structurally well-ordered but dipolar disordered crystalline phase.

Block copolypeptides with their inherent nanometer length scale of phase separation, provide means of manipulating the type (α-helices, β-strands) and persistence of peptide secondary structures. Two such examples are employed based on the α-helical poly(γ-benzyl-l-glutamate) (PBLG) polypeptide as one block and poly(l-leucine) (α-helical) or poly(O-benzyl-l-tyrosine) (POBT) (β-strands) as the second block. Although both secondary structures are present in the copolypeptides the effect of nano-scale confinement is to induce folding in the POBT β-sheets and to maintain the defected α-helices of PBLG and PLEU with a limited lateral coherence.

We present a detailed comparison of the segmental and chain dynamics of an atactic monodisperse polystyrene (molecular weight 1800 g/mol) (a-PS) studied by hierarchical multiscale molecular dynamics (MD) simulations, with an atactic polystyrene (Mn = 1644 g/mol, polydispersity index 1.14) investigated by dielectric spectroscopy, rheology and differential scanning calorimetry. The MD simulations, performed at three temperatures (403, 433, and 463 K), can capture the temperature dependence of the segmental and terminal relaxations in good quantitative agreement with experiment, taking into account the uncertainties in the development of the atomistic force field. In addition, ring and backbone segmental dynamics are studied by analyzing time-correlation functions for various bond vectors in the monomer level. MD simulations at elevated pressures (40 and 60 MPa) were also in good agreement with experiments probing the pressure-dependent glass temperature.

The effect of dipole substitution on the self-assembly, thermodynamics, and dynamics has been studied in a series of hexa-peri-hexabenzocoronenes (HBCs). The HBCs bear the same number and type of aliphatic chains, but different dipoles directly attached to the cores ranging from ∼0 to ∼3.4 D. Dipole substitution alters the energetics and reduces the transition temperature favoring the columnar hexagonal liquid crystalline phase at the expense of the crystalline phase. The equation of state was obtained by independent pressure–volume–temperature measurements in both phases that resulted in the equilibrium phase diagram. According to the latter, increasing pressure imparts stability to the crystalline phase. The molecular and supramolecular dynamics investigated, respectively, by dielectric spectroscopy and rheology, identified a hierarchy of motions comprising a fast axial motion, a slower process that completely relaxes the dipole moment, and an even slower soliton-like relaxation of structural defects.

The ion dissociation and transport properties of a series of tetrabutylammonium salts (TBA+) of rigidly dendronized anions with various sizes have been investigated in toluene, THF, and chloroform for a range of concentrations with dielectric spectroscopy and diffusion ordered spectroscopy (DOSY)-NMR. This is one of the first cases that one can study salts in low polarity solvents. The new synthetic approach increases the solubility and allows for investigation of both steric hindrance as well as electronic effects in producing weakly coordinating anions. We found that steric effects promote ion dissociation. In addition, fluorine substitution in the dendritic corona screens the electrostatic interactions and leads to increased dissociation. From the degree of dissociation and the measured diffusion coefficients, the free anion and cation diffusion coefficients were extracted and compared for the different dendrimer generations.

The dynamics of the herringbone structure formation have been studied in a monobromo hexa-peri-hexabenzocoronene derivative by infrared spectroscopy and complementary techniques. Selective probing of the vibration modes corresponding to the aromatic core and the alkyl chains, allowed investigation of their role in the phase transformation dynamics over an extraordinarily broad time-window (1–105 s). Identical kinetics were found suggesting that both the core and the alkyl chains simultaneously drive the system from the undercooled liquid crystalline to the crystalline phase with the herringbone structure.

The nematic-to-isotropic, crystal-to-nematic, and supercooled liquid-to-glass temperatures are studied in the liquid crystal 4-pentyl-4′-cyanobiphenyl (5CB) confined in self-ordered nanoporous alumina. The nematic-to-isotropic and the crystal-to-nematic transition temperatures are reduced linearly with the inverse pore diameter. The finding that the crystalline phase is completely suppressed in pores having diameters of 35 nm and below yields an estimate of the critical nucleus size. The liquid-to-glass temperature is reduced in confinement as anticipated by the model of rotational diffusion within a cavity. These results provide the pertinent phase diagram for a confined liquid crystal and are of technological relevance for the design of liquid crystal-based devices with tunable optical, thermal, and dielectric properties.Keywords: confinement; nanoporous alumina; phase transitions; rodlike liquid crystals; template synthesis

The role of alkyl chain substitution on the phase formation and core dynamics is studied in a series of diphenylamine functionalized perylenemonoimides (PMIs), by X-ray scattering, calorimetry and site-specific solid-state NMR techniques. In addition, the strong dipole associated with the donor−acceptor character of the molecules allow an investigation of the dynamics with dielectric spectroscopy. The self-assembly revealed an ordered phase only in PMIs with branched alkyl chains. This phase comprises a helical stacking of molecules with a molecular twist angle of 60°. Results from solid-state NMR further pointed out the importance of intramolecular hydrogen bonding in stabilizing the intracolumnar packing within the ordered phase. Moreover, the core dynamics are frozen as revealed by the value of the dynamic order parameters and the reduced strength of dipolar relaxation. The kinetics of phase transformation from the isotropic to the ordered phase proceeds via a nucleation and growth mechanism, and the rates are dominated by the nucleation barrier. Within the isotropic phase the core dynamics display strong temperature dependence with rates that depend on the number of methylene units in the alkyl chains.

The hierarchical self-assembly at the submicrometer, nanometer and α-helical length scales has been studied in a miktoarm star rod−coil chimera composed of poly(γ-benzyl-l-glutamate) (PBLG), polystyrene, and polyisoprene blocks by X-ray scattering, solid state NMR, and transmission electron microscopy. The propensity of the rod block toward α-helices that are further hexagonally packed gives rise to pure PBLG domains and induces the partial mixing of the two amorphous blocks. These structural results were confirmed by independent dynamic probes at the segmental and α-helical level by NMR and dielectric spectroscopy, respectively.

The effect of nanoscale confinement on the dynamics of a series of poly(n-octadecyl methacrylate)-b-poly(tert-butyl acrylate)-b-poly(n-octadecyl methacrylate) (pODMA-b-ptBA-b-pODMA) triblock copolymers, synthesized through atom transfer radical polymerization, has been investigated with dielectric spectroscopy as a function of temperature and pressure. The main effects of confinement were found in the triblocks with the more antisymmetric compositions when the radius of gyration of the confined block was comparable to the cylinder radius. It was found that the dynamics of the amorphous block accelerate upon confinement. Furthermore, confinement of the crystallizable block within cylindrical nanodomains results in the depression of the crystallization temperature.

The dynamics in poly(ethyl methacrylate) (PEMA) was studied as a function of temperature (in the range from 133.15 to 453.15 K), pressure (0.1 to 300 MPa), and molecular weight (2.0 × 103 and 1.59 × 104 g/mol) for frequencies from 3 × 10−3 to 106 Hz using dielectric spectroscopy (DS). In addition, rheological studies were made within the temperature range from 323.15 to 383.15 K. The studies reveal four dielectrically active processes—α, β, αβ, and “slow”. On lowering the temperature or increasing the applied pressure the αβ process is transformed into α and β processes. The relaxation strength of the β-process decreases markedly with increasing pressure (both above and below the glass temperature, Tg) and, for T > Tg, is accompanied by a complementary increase in relaxation strength of the α-process. The origins of the four dielectrically active processes are discussed in terms of the (i) apparent activation volume and (ii) values of the ratio of activation energies at constant volume and pressure. The latter allowed discussion of the relative contributions of thermal energy and volume to each of the dynamic processes. As a part of the paper, we derive the canonical set of equations that describe the effects of the thermodynamic variables P, V, T on the average relaxation times and these are employed to aid the interpretations of the origins of the individual relaxation processes.

The effect of pressure on the segmental dynamics in two symmetric blends of PMPS and PS is studied for pressures up to 250 MPa. In these blends, there is interplay between spinodal decomposition and glass transition, resulting in the enrichment of the high Tg component by the more mobile component. The distinctly different pressure sensitivities of PS and PMPS are used as fingerprints of the phase state, allowing for identification of the origin of the two dynamic processes arising from the PMPS segmental dynamics in PMPS-rich and PS-rich domains. Model calculations using a lattice-based equation of state lead to prediction of the phase diagram, as well as the effect of pressure on the critical temperature for the same PS/PMPS blend. The weak pressure sensitivity of the critical temperature (dTc/dP), compared to the two segmental relaxations, suggests that a transition to a thermodynamically miscible but dynamically heterogeneous state takes place for pressures above 300 MPa.

The effect of chain topology on (i) the peptide secondary structure, (ii) the nanophase self-assembly, and (iii) the local segmental and global peptide relaxations has been studied in a series of model diblock and 3-arm star copolypeptides of poly(ϵ-carbobenzyloxy-l-lysine) (PZLL) and poly(γ-benzyl-l-glutamate) (PBLG) with PZLL forming the core. Diblock copolypeptides are nanophase separated with PBLG and PZLL domains comprising α-helices packed in a hexagonal lattice. Star copolypeptides are only weakly phase separated, comprising PBLG and PZLL α-helices in a pseudohexagonal lattice. Phase mixing has profound consequences on the local and global dynamics. The relaxation of the peptide secondary structure speeds up, and the helix persistence length is further reduced in the stars, signifying an increased concentration of helical defects.

The segmental relaxation process in atactic and isotactic polypropylene (PP) is studied over the temperature (258−323 K) and pressure (0−300 MPa) ranges by means of dielectric spectroscopy. The combined dielectric and equation of state data provide a means of disentangling the relative influence of thermal energy and density on the glass “transition”. Thermal energy is the controlling parameter of the segmental dynamics in both atactic and isotactic PP as inferred by the values of the ratio of the apparent activation energies at constant pressure and volume (0.72 and 0.63, respectively). Despite the common origin of the segmental dynamics, the relaxation times of the isotactic polymer exhibit higher pressure sensitivity due to the increasing crystallinity on pressurization.

The dynamics of shape-persistent macromolecules have not been investigated to the same extent as of glass-forming liquids or amorphous polymers. Herein we investigate the dynamics of systems possessing intrinsic orientational order. Do such systems exhibit a glass transition and if yes, what is its origin? Do they show a dual relaxation scenario (α- and β-processes) as glass-forming liquids and polymers? If such processes exists what is their pressure dependence? Is the α-process controlled by temperature or by the available (free) volume? To answer these fundamental questions we employ some of the most common polymers exhibiting intrinsic orientational order, namely: (a) side-chain liquid crystalline polymers, (b) hairy-rod polymers and (c) synthetic polypeptides with α-helical secondary structure. We show that these molecularly diverse but shape-persistent macromolecules share some common features in their dynamic response.