Control of Mechanical Behavior in Polyolefin Composites:  Integration of Glassy, Rubbery, and Semicrystalline Components

Abstract

The mechanical properties of a homologous series of polyolefin block copolymers comprised of glassy poly(cyclohexylethylene) (C), elastomeric poly(ethylene-alt-propylene) (P), and semicrystalline poly-(ethylene) (E) are documented. Monodisperse CPEPC, CPE, and CEPEC with mass fractions w C ∼ 0.39-0.44 and 0 e e 1, where ) w E /(w E + w P ), were synthesized by sequential anionic polymerization of styrene, isoprene, and butadiene followed by catalytic hydrogenation. These materials hierarchically microphase separate into lamellae, within which templated crystallization-induced segregation occurs. As increases, the unoriented, polydomain CPEPC materials exhibit monotonically increasing elastic moduli and yield stresses, comparable ultimate tensile strengths, and decreasing failure strains. Cold drawing the CPEPC polymers yields high-strength materials, the structures of which are examined by small-and wide-angle X-ray scattering. Drawn CPEPC-70 ( ) 0.70) exhibits improved toughness with an ultimate tensile strength σ fail ) 75 ( 10 MPa and elongation at break of fail ) 1.22 ( 0.22, as compared to σ fail ) 92 ( 21 MPa and fail ) 0.86 ( 0.18 for drawn CEC ( ) 1.00). Elasticity measurements on the drawn samples demonstrate that materials with > 0 exhibit low degrees of stress softening, while smaller permanent sets and higher failure strains are observed as decreases.

Novel Nanostructures from Self‐Assembly of Chiral Block Copolymers

“…In order to extend the number of varieties of self-assembled nanostructures of BCPs, various approaches have been tried, such as crystallizing semicrystalline BCPs, [35][36][37] selfassembling liquid crystalline BCPs, [38,39] ABC triblock terpolymers [14][15][16] and star copolymers, [40][41][42][43] as well as functionalizing constituent blocks. [44][45][46] Among these, a straightforward way to modify the performance of a BCP is through crystallization of the constituted blocks.…”

Thermodynamic characteristics of poly(cyclohexylethylene‐b‐ethylene‐co‐ethylethylene) block copolymers

“…The percent crystallinity of the softer PE domains strongly affects essentially all the properties of the PCHE‐based block copolymers, notably the optical and mechanical properties. To study the effect of glassy, rubbery, and semicrystalline block copolymers, Mahanthappa et al8 made a series of CPEPC pentablock materials, in which the central soft portion of the molecules, PEP, was systematically varied from pure semicrystalline E ( x = 0.07) to pure rubbery “P”. They found that percent crystallinity of the E block increased as the amount of P increased, which was attributed to a reduction in the configurational constraints placed on the PE blocks within the soft domains.…”

RAFT‐Based Synthesis and Characterization of ABC versus ACB Triblock Copolymers Containing tert‐Butyl Acrylate, Isoprene, and Styrene Blocks

“…As a functional material, polyisoprene represents a wide variety of options. It is degradable under ozonolysis conditions,32, 33 can be crosslinked by a variety of chemistries including radical,34 hydrosilylation,3 and sulfide formation,4, 7 and offers many opportunities for functionalization (e.g., via hydrochlorination,32 hydrogenation,35 epoxidation,36 etc.). Polyisoprene is also interesting for its low T g , which can be tuned by the polyisoprene regio‐ and stereochemistry and also by chemical modification of previously prepared polyisoprene.…”