Morphology nanofibrils

Keywords Bands Morphology Nanofibrils Poly(tetrafluorethylene) Single crystals Shish kebabs... 

Kaneko T, Higashi M, Matsusaki M et al (2005) Self-assembled soft nanofibrils of amphi-pathic polypeptides and their morphological transformation. Chem Mater 17 2484—2486... 

As mentioned previously, mesoscale crystalline morphologies and molecular orientation of HT-PATs in solution-deposited films can be controlled through different solution-processing methods and subsequent thermal treatments [15,17,23,35,36,44,59,89]. Figures 5.2.18 and 5.2.19 represent typical examples for tunable crystalline morphologies and molecular orientations of HT-PHT in solution-deposited films. First, in terms of mesoscale morphologies, HT-PHT (M = 18.8 kDa) films drop-cast from CHCI3 show weU developed nanofibrils interconnected with each other, while the spin-cast... 

The A. coerulea material was poorly crystalline, showing a broad peak at 20° 20, but the spectrum for the alkali-treated material showed a broad peak at 10.72° and two peaks at 18.72° and 19.98° 20, with close similarity to the spectrum of authentic chitosan. Optical microscopy showed that the alkali-treated products, stained with Saphranine or with other stains, preserved the morphology of the fungus, with flattened and empty structures [30] (Fig. 1). This work introduced the concept that an extended surface area of the carbohydrate polymer leads to enhanced performance, as amply confirmed by most recent works dealing with chitin and chitosan nanofibrils. In fact, the partially re-acetylated chitosan (degree of acetylation 0.23) is promptly depolymerized by lysozyme, papain, and lipase thanks to the ideal degree of acetylation for maximum enzymatic activity. Remarkably, the re-acetylated... 

The rod-like morphology of the nanofibrils supports the high yields, because a-chitin nanofibrils prepared by acid hydrolysis from TEMPO-mediated oxidation have a spindle-like shape and a larger distribution range of widths. 

Scientists have fabricated scaffolds in a two-step approach that combines an in situ coprecipitation synthesis route with the electrospinning process to prepare a novel type of biomimetic nanocomposite nanofibres of HA/CHT. The electrospun composite nanofibres of HA/CHT, with compositional and structural features close to the natural mineralised nanofibril counterparts, are of potential interest for bone TE. The results of HA/CHT indicate that although an initial inhibition occurs, the nanofibrous scaffolds which contained HA, as compared to scaffolds of CHT alone, appeared to have significantly stimulated the bone forming ability as shown by the cell proliferation, mineral deposition, and morphological observations, due to the excellent osteoconductivity of HA [19, 34, 56, 70]. 

If the two blend partners are not capable of forming hydrogen bonds, as is the case of the majority of studied blends ([12-21], e.g.. Figure 9.4), the final material is in the form of individual non-interconnected nanofibrils. This is the same situation as the one that is observed with the blend of PBT with PP (Figure 9.7c,d), where the final nano-morphology represents continuous, not interconnected individual nanofibrils with diameter of about 250 nm (Figure 9.7d). 

In addition to the outlined morphological difference between the two types of polymer blends, without and with hydrogen bonding between the blend partners, it turned out that the mechanism of formation of the nano-sized materials is completely different for the one or the other case. Detailed studies on the mechanism of formation of the individual micro- and nanofibrils led to the conclusion that it takes place during the cold drawing via coalescence of the elongated droplets [18], as schematically illustrated in Figure 9.9. 

Keywords Biopolymers Calcium carbonate Cellulosic fibrils Composites Coprecipitation Micro- and Nanofibrillated cellulose Morphology Pigments Properties... 

Elementary chlorine-free (ECF)-bleached unrefined softwood pulp obtained from a mill in southern Finland was grotmd in a Supermass colloider " to produce fines. The Bauer-McNett analysis of the fines showed that 92% of the fines passed through the 200 mesh. The consistency of the produced fines-PCC composite was in the range of 0.085-0.1%. Calcium hydroxide was mixed to obtain 2 1 PCC nanofibrils and carbonised to crystallise PCCs with colloidal, rhombohedral, and scalenohedral morphologies. 

In a different study, gel-drawn ultrahigh molecular weight PE was analyzed by SFM. The images showed different well-defined levels of the underlying fibrillar morphology (132). These include bundles of microfibrils (diameter between 4 and 7 /um), microfibrils (diameter between 0.2 and 1.2 / m), nanofibrils, and regular chain patterns on the molecular level (Fig. 19). 

The fact that the MFC concept offers the possibility to isolate neat micro- or nanofibrils via selective dissolution of the second blend component offers other interesting apphcations. In addition, the suggested method for conversion of the bulk polymers into nano-sized materials allows control of the final nano-morphology. The latter can be in... 

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