Phase Behavior of Polystyrene and Poly(n-pentyl methacrylate) Blend with Small Amounts of Symmetric Polystyrene-block-poly(n-pentyl methacrylate) Copolymers

Toughening mechanism behind intriguing stress–strain curves in tensile tests of highly enhanced compatibilization of biodegradable poly(lactic acid)/poly(3-hydroxybutyrate-co-4-hydroxybutyrate) blends

The intriguing mechanical properties and mechanism of highly enhanced compatibilization of two biopolymer blends.

Side-Chain Supramolecular Polymers Employing Conformer Independent Triple Hydrogen Bonding Arrays

Derivatives of thymine have been extensively used to promote supramolecular materials assembly. Such derivatives can be synthetically challenging to access and may be susceptible to degradation. The current article uses a conformer-independent acceptor-donor-acceptor array (ureidopyrimidine) which forms moderate affinity interactions with diamidopyridine derivatives to effect supramolecular blend formation between polystyrene and poly(methyl methacrylate) polymers obtained by RAFT which have been functionalized with the hydrogen bonding motifs.

Kinetically trapped co-continuous polymer morphologies through intraphase gelation of nanoparticles

We describe an approach to prepare co-continuous microstructured blends of polymers and nanoparticles by formation of a percolating network of particles within one phase of a polymer mixture undergoing spinodal decomposition. Nanorods or nanospheres of CdSe were added to near-critical blends of polystyrene and poly(vinyl methyl ether) quenched to above their lower critical solution temperature. Beyond a critical loading of nanoparticles, phase separation is arrested due to the aggregation of particles into a network (or colloidal gel) within the poly(vinyl methyl ether) phase, yielding a co-continuous spinodal-like structure with a characteristic length scale of several micrometers. The critical concentration of nanorods to achieve kinetic arrest is found to be smaller than for nanospheres, which is in qualitative agreement with the expected dependence of the nanoparticle percolation threshold on aspect ratio. Compared to structural arrest by interfacial jamming, our approach avoids the necessity for neutral wetting of particles by the two phases, providing a general pathway to co-continuous micro- and nanoscopic structures.

Two-Dimensional Heterospectral Correlation Analysis of Wide-Angle X-ray Scattering and Infrared Spectroscopy for Specific Chemical Interactions in Weakly Interacting Block Copolymers

We investigated, via two-dimensional heterospectral correlation analysis of wide-angle X-ray scattering (WAXS) and infrared (IR) spectroscopy, the specific chemical interactions existing in weakly interacting polystyrene-block-poly(n-pentyl methacrylate) copolymers (PS-PnPMA). PS-PnPMA was shown to exhibit a closed-loop-type phase behavior, where, upon heating, a lower disorder-to-order transition (LDOT) was found at lower temperatures, and an upper order-to-disorder transition (UODT) was observed at higher temperatures. The specific interaction between the PS and PnPMA blocks mainly arises from the dipole in the benzene ring of PS and the induced dipole in the PnPMA due to cluster formation with a size of 1 approximately 2 nm. We found that the synchronous 2D WAXS-IR heterospectral correlation spectrum of the ordered state was completely different from that in the two disordered states. The CH group of the main chains of PS and PnPMA did not contribute to the cluster formation in the two disordered states, indicating that the main chains of PS and PnPMA blocks were randomly distributed in the two disordered states. However, only the C=C group in the PS block contributed to the cluster at a disordered state below the LDOT, whereas both the C-C-O group in PnPMA and the entire phenyl ring and C=C group in PS contributed to cluster formation at another disordered state above the UODT. Thus, the probability that PS (and PnPMA) chains were located at their own neighboring chains at one disordered state above the UODT is larger than that at another disordered state below the LDOT.