Linear viscoelastic response and melt microstructure of ultra-high molecular weight poly(α-olefins) (UHMW PO) with bottlebrush architectures, from poly(1-hexene) to poly(1-octadecene) synthesized by metal coordinative insertion polymerization, were measured as a function of side-chain length, N sc . All these bottlebrush POs are highly entangled, with an average number of entanglements per chain, Z, greater than 50, which allows accurate determination of their rubbery plateau moduli, G N 0 , and their entanglement molecular weights, M e . Their plateau moduli scale with their side-chain lengths as G N 0 ∼ N sc −1.47 , in agreement with the scaling theory for the dense bottlebrush limit that predicts. Melt structures of these bottlebrush poly(1-olefin)s and their melt structural changes with temperature were determined by wide-angle X-ray scattering. Concomitant with thermal expansion of these bottlebrush PO melts is a nonmonotonic change in backbone-to-backbone distance (d 1 ) and a monotonic increase in side-chain spacing (d 2 ). Both the melt-flow interchain friction coefficient and the viscosity of these UHMW PO bottlebrushes show a very strong dependence on d 2 , characterized by two exponential decay regimes, with decay constants having an exponential dependence on N sc .

We investigate the microstructure and linear viscoelasticity of model molecular bottlebrushes (BBs) using rheological and small-angle X-ray and neutron scattering measurements. Our polymers have short atactic polypropylene (aPP) side chains of molecular weight ranging from 119 g/mol to 259 g/mol and narrow molecular weight distribution (Mw/Mn 1.02–1.05). The side chain molecular weights are a small fraction of the entanglement molecular weight of the corresponding linear polymer (Me,aPP= 7.05 kg/mol), and as such, they are unentangled. The morphology of the aPP BBs is characterized as semiflexible thick chains with small side chain interdigitation. Their dynamic master curves, obtained by time-temperature superposition, reveal two sequential relaxation processes corresponding to the segmental relaxation and the relaxation of the BB backbone. Due to the short length of the side chains, their fast relaxation could not be distinguished from the glassy relaxation. The fractional free volume is an increasing function of the side chain length (NSC). Therefore, the glassy behavior of these polymers as well as their molecular friction and dynamic properties are influenced by their NSC values. The apparent flow activation energies are a decreasing function of NSC, and their values explain the differences in zero-shear viscosity measured at different temperatures.

The coordinate transformation (CT) method was applied to measure the local curvature of the interface of an immiscible polymer blend made of fluorescently labeled polystyrene (FLPS) and styrene-ran-acrylonitrile copolymer (SAN). The CT method involves the local parametrization of the interface by a quadratic polynomial to compute the local values of the mean (H) and the Gaussian (K) curvatures. Distributions of the curvatures at different annealing times were obtained by measuring H and K at many (typically 10(7)) points on the interface. Coarsening of a symmetric (50/50 w/w FLPS/SAN) and a nonsymmetric (35/65 w/w) blend was monitored. For the symmetric blend, two regimes of surface evolution were identified: in the early stage, the probability densities of the curvatures at various times were successfully scaled by a time-dependent characteristic length, i.e., interface area per unit volume (Q). This behavior has been previously observed in blends with morphologies created by a different mechanism, namely spinodal decomposition. In the late stage, the dynamic scaling failed and the time evolution of the interface slowed down. For the nonsymmetric blend, the domains of the minor phase (FLPS) were more elongated and they eventually broke up producing a composite microstructure with islands of drops within cocontinuous domains. We defined a "scaled" genus (G) to quantify the topology evolution of the blends during coarsening. Loss of connectivity was evidenced by a decrease of G with time for the nonsymmetric blend, while a constant value of this parameter indicated no change in topology during coarsening for the symmetric blend.

Isotactic and atactic poly(1-octadecene) (iPOD and aPOD) have been synthesized by organometallic coordinative insertion polymerization of 1-octadecene. Analyzing X-ray and neutron scattering data of POD melts identifies their bottlebrush structures as flexible rods where the rod length is the extended backbone length and rod radius is the side chain coil dimension. Upon cooling, both iPOD and aPOD melts crystallize by fully extending their coiled side chains to form orthorhombic alkane crystals in iPOD and nematically ordered rotator alkane crystals in aPOD, as determined by X-ray scattering and Raman spectroscopy. Molecular dynamics simulations of isotactic and atactic 48-mers of 1-octadecene were applied to define and verify melt and crystalline structures and scattering peak assignments, respectively. Modeling suggests that side chains of both crystallized isotactic and atactic PODs align at 70°and 160°to the 4/1 spiral backbone of equal probability, at an average of 115°, and POD chains pack in an antiparallel pattern. Large wheat-sheaf structural assembly of fibril bundles can be observed in aPOD, which render high opacity to these samples. Each of those fibrils is made of several bottlebrush molecules packed into a hexagonal lattice. Faster crystallization observed in iPODs hinders the formation of large crystallites, which results in translucent samples.

Cocontinuous morphologies of polymer blends are thermodynamically unstable: they will coarsen when held above their glass or melting transition temperature. We have found that properly chosen diblock copolymers (bcp) can arrest coarsening during quiescent annealing. The effects of bcp on the cocontinuous morphologies of polystyrene (PS)/polyethylene (PE), PS/poly(methyl methacrylate) (PMMA) and PS/styrene-ran-acrylonitrile copolymer (SAN) blends were studied using scanning electron microscopy (SEM) and laser scanning confocal microscopy (LSCM) with image analysis. Bcp effectiveness was dependent on copolymer molecular weight, concentration, and asymmetry. Our interpretation emphasizes the role of bcp micelle creation and destruction as potential bottlenecks in the kinetics of interfacial adsorption of copolymer during mixing and of interfacial desorption during coarsening. In cases where adsorption and desorption appear to be facile, our results for the rate of coarsening are consistent with equilibrium predictions from self-consistent field theory for the dependence of interfacial tension upon copolymer asymmetry. We show that the coarsening of cocontinuous blends can provide a method to quantify the reduction in interfacial tension due to block copolymer addition, which is difficult to measure by conventional methods.