Crystalline and Spherulitic Morphology of Polymers Crystallized in Confined Systems

Abstract

Due to the effects of microphase separation and physical dimensions, confinement widely exists in the multi-component polymer systems (e.g., polymer blends, copolymers) and the polymers having nanoscale dimensions, such as thin films and nanofibers. Semicrystalline polymers usually show different crystallization kinetics, crystalline structure and morphology from the bulk when they are confined in the nanoscale environments; this may dramatically influence the physical performances of the resulting materials. Therefore, investigations on the crystalline and spherulitic morphology of semicrystalline polymers in confined systems are essential from both scientific and technological viewpoints; significant progresses have been achieved in this field in recent years. In this article, we will review the recent research progresses on the crystalline and spherulitic morphology of polymers crystallized in the nanoscale confined environments. According to the types of confined systems, crystalline, spherulitic morphology and morphological evolution of semicrystalline polymers in the ultrathin films, miscible polymer blends and block copolymers will be summarized and reviewed.

Soft X-ray Spectromicroscopic Evidence for Site-Specific Nanoscale Phase Segregation of Polyurethane onto a Confined Surface

“…From Porod’s analysis, one may find the average size of the domain, which predominantly consists of the hard phase, and the domain size is relatively increased due to π–π stacking as well as polar and hydrogen bonding interactions on the functional nanofiller surface, as shown in Scheme , and was also found by thermal and mechanical analysis earlier. , The functionalized MWCNTs used here are of average 20 nm diameters and 2 μm lengths, whereas functionalized few-layer graphenes are of average 2 μm diameters and 1–2 nm thick, where the unique feature of a crumpling graphene sheet inside the polymer matrix produced a higher domain size, which we also found during the phase separation of TPU nanocomposites during electrospinning. , The nanofillers were reported to act as a platform to interconnect the different small-sized hard segments, where the hard segment size is generally much lower than the length of the nanofillers . The pristine PU hard segment domain size is calculated to be 8 nm, which is lower than that reported earlier and could be attributed to the hindrance of growth of hard segments in the confined thin-film geometry. , …”

“…44 The pristine PU hard segment domain size is calculated to be 8 nm, which is lower than that reported earlier 45 and could be attributed to the hindrance of growth of hard segments in the confined thin-film geometry. 4,46 We then used X-ray absorption spectromicroscopy with a submicron resolution to study the electronic interaction of hard segments around the nucleating sites of carbon atoms in the supporting platform of nanomaterials, which are represented in Figures 5−7. The different regions of interest (ROI) in the position away, near, and on the hard phaseseparated geometry with contrast below and above the carbon edge have been selected for the X-ray absorption near-edge structure (XANES) spectrum in 275−310 eV with 1 eV below edge jump, followed by 0.2 eV for the main region.…”

Exploring Morphological Effects on the Mechanics of Blended Poly(lactic acid)/Poly(ε-caprolactone) Extruded Fibers Fabricated Using Multilayer Coextrusion

“…These findings suggest that PCL accelerated nucleation growth of the PLA crystallites, but PLA inhibited the nucleation of PCL crystallites. Additionally, the changes in the crystallite size may have been a result of morphological confinement imparted on the PLA and PCL phases …”

Nanostructured Polymer Monoliths for Biomedical Delivery Applications

“…A second factor contributing to the relatively constant domain spacing upon hPEO addition is the crystallization of PEO in these blended monoliths. − The degree of crystallinity of PEO in monoliths is listed in Table S1, which was determined by crystallinity ( X c ) = Δ H m (measured)/Δ H m (100%), where Δ H m (measured) and Δ H m (100%) are the heat of melting for PEO in monoliths measured from DSC (see Figure S5), calculated based on the PEO content in monoliths before and after release and that of 100% crystalline PEO (196.8 J/g), respectively. The addition of 2000 g/mol hPEO to the pure block polymer monolith formulation (PEO-CTA:S/DVB = 8:17, 20 kg/mol PEO-CTA) increased the overall PEO crystallinity from 39 to 62% in the hPEO:PEO-CTA = 1:1, consistent with the previous research on a poly­(ethylene oxide)/poly­(2-vinylpyridine)- b -(ethylene oxide) (PEO/P2VP- b -PEO) blend .…”