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Nucleating agents (NAs) are widely used for speeding up processing and tuning the final optical and mechanical properties. Despite their industrial importance, the search for highly efficient NAs is still mainly empirical. In this work, the heterogeneous nucleation process of isotactic polypropylene (i-PP) droplets containing nucleating agents (i.e., sodium benzoate (SB), (4,6-di-tert-butylphenyl)phosphate (NA-11), quinacridone quinone (QQ)) dispersed in an immiscible polystyrene matrix has been studied by differential scanning calorimetry (DSC) using an isothermal step crystallization protocol. When semicrystalline polymers are confined into isolated micro-or nanodomains, nucleation can kinetically control the overall crystallization. Differently, in a bulk polymer, the contributions of the nucleation and growth steps to the overall crystallization rate are commonly of similar importance. In the studied system, it is shown for the first time that the crystallization of nucleated i-PP droplets exhibits a first-order kinetics, with characteristic times much larger than those required for the crystals to grow and occupy the whole microdomain volume. Therefore, the kinetics of heterogeneous nucleation can be directly assessed. On the contrary, when neat i-PP droplets are self-nucleated, the crystallization kinetics shows a sigmoidal trend, with times comparable to those for the crystal space filling. This indicates the absence of any primary nucleation barrier for ideally self-nucleated PP melts, or at least that this nucleation barrier is negligible in comparison to the one for secondary nucleation/crystal growth. For the first time, it is evidenced that, as long as nucleation is the rate-determining step in the overall crystallization kinetics, a first-order kinetics can be obtained for both homo-or heterogeneously nucleated droplets in immiscible blends. A novel way to calculate an "intrinsic" nucleation efficiency, based on the derived freeenergy barriers of the different NAs, is proposed. This fundamental knowledge of heterogeneous nucleation can serve as a tool for a more rational search for new nucleating agents and can provide a method to unambiguously identify the origin of multiplecrystallization exotherms in fractionated crystallization of immiscible blends.

Protein adsorption has a vital role in biomaterial surface science because it is directly related to the hemocompatibility of blood-contacting materials. In this study, monomethoxy poly(ethylene glycol) (mPEG) with two different molecular weights was grafted on polyethylene as a model to elucidate the adsorption mechanisms of plasma protein through quartz crystal microbalance with dissipation (QCM-D). Combined with data from platelet adhesion, whole blood clotting time, and hemolysis rate, the blood compatibility of PE-g-mPEG film was found to have significantly improved. Two adsorption schemes were developed for real-time monitoring of protein adsorption. Results showed that the preadsorbed bovine serum albumin (BSA) on the surfaces of PE-g-mPEG films could effectively inhibit subsequent adsorption of fibrinogen (Fib). Nonspecific protein adsorption of BSA was determined by surface coverage, not by the chain length of PEG. Dense PEG brush could release more trapped water molecules to resist BSA adsorption. Moreover, the preadsorbed Fib could be gradually displaced by high-concentration BSA. However, the adsorption and displacement of Fib was determined by surface hydrophilicity.

An efficient approach to the organic functionalization of multiwalled carbon nanotubes (MWCNTs) for the production of highly soluble/dispersible materials has been accomplished by a class of highly reactive and thermally stable nitrones. Besides the unprecedented solubility in aprotic polar solvents of the functionalized samples (up to 10 mg of f-MWCNTs per mL of DMF), we have demonstrated, for the first time, that the CNT functionalization by nitrones preferentially occurs at the defective CNT sidewalls without any appreciable degradation of their sp2 network. The role of the reticular imperfections on the graphitic lattice of the MWCNTs has been experimentally and theoretically addressed. A complete chemical (TGA-MS, FT-IR, SSA) and morphological (TEM, AFM) characterization of the functionalized materials has accounted for the high degree of CNT functionalization, whereas Raman scattering, in combination with complementary XRPD and active surface area (ASA) measurements, has provided unambiguous evidence of the key role played by the structural “disorder” of the MWCNTs in the nitrone cycloaddition. Density functional theory (DFT) calculations on the reactivity of selected topological defects at the CNT sidewalls have contributed to trace-out a “defect-based” sidewall reactivity trend. The excellent processability of the functionalized MWCNTs has been finally exploited for the preparation of highly homogeneous CNT/polymer nanocomposites with CNT loadings as high as 3 wt%

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