Microphase separation of bio-based soft blocks in a hard isosorbide polycarbonate enabled the preparation of a transparent bio-based engineering plastic with improved mechanical properties and processability at milder conditions. The ability to process these isosorbide-containing polycarbonates at lower temperatures in combination with a lower polymerization temperature due to the use of the activated bis(methyl salicyl) carbonate as the carbonate source avoided the undesired elimination of β-hydrogens, which is commonly observed in isosorbide-containing polymers. Preparation of a wide range of custom samples with varying combinations of soft blocks, followed by characterization and statistical analysis, enabled the identification of the correlations between composition and mechanical and thermal properties, resulting in an optimized engineering plastic with facile processing, transparency, and ductility combined with >84% renewable content.
Detailed knowledge on structural
information is required to derive
the rheological properties of branched polymers. Size-exclusion chromatography
with triple-detection (TD-SEC), comprising a concentration, a light
scattering, and a viscosity detector, is a powerful tool to analyze
the degree of branching of polymers as a function of their molar masses.
However, TD-SEC alone is incapable of fully deconvoluting complex
polymer systems. In this study we discuss a more sophisticated approach
that includes coupling of TD to our recently described novel online
two-dimensional liquid chromatography method (2D-LC), based on solvent
gradient at near-critical conditions in the first dimension. Thus,
a contour plot of the branching ratio is presented, and unique detailed
information on the degree of branching can be derived for branched
polycarbonate (PC) sample. Furthermore, the molar mass distributions
of separated linear and branched PC chains as well as their fractions
in the polymer are quantified. The corresponding data are correlated
to Monte Carlo simulations of the polycondensation process of a branched
PC, and both methods show a high level of agreement in the determined
molar mass distributions of the linear and branched PC chains as well
as their fractions. Finally, the influence of chemical structure on
rheological properties is demonstrated.
Photochromic dyes have restricted use in rigid polycarbonates because of slow coloration and decoloration kinetics. In this study, it is shown that the decoloration kinetics of two photochromic dyes can be controlled by tuning the chain stiffness and free volume of the host matrix. The introduction of flexible moieties in rigid BPA-based polycarbonate chain accelerates the decoloration of these dyes whereas a rigid comonomer delays the decoloration kinetics. Although T g might be used as a parameter to improve photochromism in polymer matrices, dynamic mechanical analysis demonstrates that the decoloration kinetics of the dyes in host polymer matrices having similar T g depends primarily on the secondary relaxations and, thus, on the polymer architecture. The effect of the comonomer type on the characteristic ratio is also discussed underlining the potential relationship between the free volume and chain stiffness. These results open the possibility to develop transparent or semitransparent photochromic materials based on tailor-made co-polycarbonates.
The paper discusses the relationship between rheology and morphology of immiscible polypropylene (matrix))/polycarbonate (dispersed phase) blends compatibilized with novel polypropylene-polycaprolactone block and graft copolymers. Transmission electron microscopy (TEM) experiments revealed uniform droplet morphologies and a reduction of the average size of the dispersed phase upon addition of the compatibilizer. The results suggested the influence of the molecular weight distribution (MWD)/chemical composition distribution (CCD) and topology of the compatibilizer on the compatibilizing performance. Graft copolymers were found to be most effective in reducing the size of the dispersed phase, whereas the performance of block copolymers appeared to be highly dependent on the block length of PP. Small-amplitude oscillatory rheological experiments revealed an increase in elasticity at low frequencies caused by the interfacial interactions induced by the compatibilizer. The effect was quantified using the relaxation time spectrums that displayed the additional peak at longer relaxation times via Gramespacher-Meissner method. Broadband dielectric spectroscopy (BDS) revealed the influence of the copolymer architecture and molecular weight of the polypropylene blocks on the properties of the interfacial polarization, which was in line with both rheology and morphology data.
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