Scanning electron microscopy polymerization

In 1994, we reported the dispersion polymerization of MM A in supercritical C02 [103]. This work represents the first successful dispersion polymerization of a lipophilic monomer in a supercritical fluid continuous phase. In these experiments, we took advantage of the amphiphilic nature of the homopolymer PFOA to effect the polymerization of MMA to high conversions (>90%) and high degrees of polymerization (> 3000) in supercritical C02. These polymerizations were conducted in C02 at 65 °C and 207 bar, and AIBN or a fluorinated derivative of AIBN were employed as the initiators. The results from the AIBN initiated polymerizations are shown in Table 3. The spherical polymer particles which resulted from these dispersion polymerizations were isolated by simply venting the C02 from the reaction mixture. Scanning electron microscopy showed that the product consisted of spheres in the pm size range with a narrow particle size distribution (see Fig. 7). In contrast, reactions which were performed in the absence of PFOA resulted in relatively low conversion and molar masses. Moreover, the polymer which resulted from these precipitation... 

Figure 12.7 Photographs of electrospun fiber mats embedded with 1 (a) before and (b) after 254-nm UV irradiation (1 mW/cm ) for 3 min. (c) Scanning electron microscopy image of the microfibers containing polymerized 1. (c) Photographs of the polydiacetylene-embedded electrospun fiber mats prepared with various diacetylene monomers after exposure to organic solvent. Reprinted fi om Yoon et al. (2007). Copyright 2007 American Chemical Society. (See color insert.)...

In addition to enzymatic hydrolysis of natural lipids in polymeric membranes as discussed in chapter 4.2.2., other methods have been applied to trigger the release of vesicle-entrapped compounds as depicted in Fig. 37. Based on the investigations of phase-separated and only partially polymerized mixed liposomes 101, methods to uncork polymeric vesicles have been developed. One specific approach makes use of cleavable lipids such as the cystine derivative (63). From this fluorocarbon lipid mixed liposomes with the polymerizable dienoic acid-containing sulfolipid (58) were prepared in a molar ratio of 1 9 101115>. After polymerization of the matrix forming sulfolipids, stable spherically shaped vesicles are obtained as demonstrated in Fig. 54 by scanning electron microscopy 114>. 

The hole formation in the liposomal membrane after treating the vesicles with reducing agents can be demonstrated by the fast and complete release of eosin, a fluorescent marker. Final proof that the polymeric backbone of the uncorked vesicles does not collapse comes from scanning electron microscopy. Fig. 56 shows the spherical structure of the liposomes with holes. 

The determination of the evolution of concentrations of different species and functional groups enables one to discern different paths present in the reaction mechanism. For example, Fig. 5.13 shows that as the molar ratio of styrene to polyester C=C double bonds (MR) increases from 1/1 to 4/1, the curves tend to shift downward. For MR = 4/1 there is a very low styrene consumption until the polyester double bonds are converted to 40%. On the other hand, SEM (scanning electron microscopy) shows phase separation of a UP-rich phase in the early stages of the polymerization. Most radicals are probably trapped in this phase, which explains the higher initial conversion of the UP double bonds than styrene double bonds. A kinetic model would have to take this observation into account. 

Lednicky F et al. (1991) Silicone rubber-hydrogel composites as polymeric biomaterials. Ill An investigation of phase distribution by scanning electron microscopy. Biomaterials 12(9) 848—852... 

Another possible evidence of grafted organic/polymeric molecules onto CNT surface can be achieved by microscopy analyses using both principal types of electron microscopy - transition electron microscopy, TEM, or scanning electron microscopy, SEM (15,19,24,44,45,47). Such analyses are usually performed after careful extraction of the polymer from tubes by polymer solvents, performed several times by a reflux procedure with an excess of solvent therefore it is supposed that only covalently attached molecules remain fixed at CNT surface. High Resolution mode of TEM analysis shows the evidence of amorphous material on nanotubes surface (15). 

This paper reports on radical polymerization of MMA in phenolic resol and confirmation of the structure by measurement of d3mamic mechanical properties, scanning electron microscopy, and tensile tests, then the damping ability of these vinyl compound/phenolic IPNs is evaluated. 

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