Polymer micrograph

It was noted in early session that sphemlitic structure of a polymer affects the mechanical properties of the polymer. Micrographs of PHB and PHB12 V crystals stractrrre, revealed using POM, are shown in Figure 12. The PHB V and PHBHHx show fine fibrillar structure of spherulites while PHB shows circular ring banded spherulites, both types of crystals display Maltese cross. 

Note that a statistical study could be done on an electron micrograph like that shown in Fig. 1.1. The dimensions of the blobs could be converted to volumes and then to masses with a knowledge of the density of the deposited polymer. This approach could be organized into a table of classified data from which any of these averages could be calculated. 

Figure 4.11 Electron micrographs of polyethylene crystals, (a) Dark-field illumination shows crystals to have a hollow pyramid structure. (Reprinted with permission from P. H. Geil, Polymer Single Crystals, Interscience, New York, 1963.) (b) Transmission micrograph in which contrast is enhanced by shadow casting [Reprinted with permission from D. H. Reneker and P. H. Geil, /. Appl. Phys. 31 1916 (I960).]...

The electron micrographs of Fig. 4.11 are more than mere examples of electron microscopy technique. They are the first occasion we have had to actually look at single crystals of polymers. Although there is a great deal to be learned from studies of single crystals by electron microscopy, we shall limit ourselves to just a few observations ... 

Fig. 8. Electron micrograph of Merino wool fibers in a fabric that have been treated with a typical shrink-resistance polymer, showing fiber—fiber bond...

Fig. 11. Micrographs of iastant films la cross section, swelled in 5% Na2S04 to reveal detail (lOOOX). Figures in parentheses indicate the approximate thickness of the swelled section relative to that of a nonsweUed section, (a) Polacolor ER (2.OX) (b) Fuji FP-lOO (1.5X) (c) Spectra film (1.3X). The sphere visible in (b) is a polymer bead of a type used in surface layers to prevent blocking.

Fig. 8. Electron micrograph.s showing the interface between polystyrene (top) and a styrene-isoprene diblock polymer (bottom), annealed at I50°C for the times shown. Isoprene units are stained and appear black) (reproduced from [31], copyright American Chemical Society).

Figure 1 The transmission electron micrographs of the crosslinked products of MCI cast from benzene, (a) at a 0.05 wt% polymer concentration and shadowed with Cr at an angle of 20°, and (b) at a 0.05 wt% concentration [24].

Figure 2 The transmission electron micrographs of samples cast from solution containing 1 wt% of polymer, (a) the block copolymer BCl, and (b) the microsphere, MCI [24].

The results of mechanical properties (presented later in this section) showed that up to 20 phr, the biofillers showed superior strength and elongation behavior than CB, cellulose being the best. After 30 phr the mechanical properties of biocomposites deteriorated because of the poor compatibility of hydrophilic biopolymers with hydrophobic natural rubber(results not shown). While increasing quantity of CB in composites leads to constant increase in the mechanical properties. Scanning electron micrographs revealed presence of polymer-filler adhesion in case of biocomposites at 20 phr. 

The results of the mechanical properties can be explained on the basis of morphology. The scanning electron micrographs (SEM) of fractured samples of biocomposites at 40 phr loading are shown in figure. 3. It can be seen that all the bionanofillers are well dispersed into polymer matrix without much agglomeration. This is due to the better compatibility between the modified polysaccharides nanoparticles and the NR matrix (Fig. 4A and B). While in case of unmodified polysaccharides nanoparticles the reduction in size compensates for the hydrophilic nature (Fig. 3C and D). In case of CB composites (Fig. 3E) relatively coarse, two-phase morphology is seen. 

FIGURE 38.10 Transmission electron micrograph of styrene-co-acrylonitrile/acrylonitrile butadiene mbber/ waste NBR (SAN/NBR/w-NBRybased thermoplastic elastomer (TPE). (Reprinted from Anandhan, S., De, P.P., Bhowmick, A.K., Bandy opadhyay, S., and De, S.K., J. Appl Polym. Sci., 90, 2348, 2003. With permission from Wiley InterScience.)... 

Figure 6 Micrographs of drawn samples of polyethylene films of Mw = 1.5 X 10 and Mn = 2 x 10 crystallized from solutions in decalin, and from the melt (see Reference 1 for details). The initial polymer volume fractions were (a) - 0.005 (b) - 0.02 (c) - 0.1 (d) - 1.

FIGURE 12 Scanning electron micrograph of contraceptive vaccine microspheres based on lactide/glycolide polymer. 

FIGURE 17 Scanning electron micrograph (30x) of polymer rods (2.4 X 20 mm prepared from 3,9-bis(ethylidene-2,4,8,10-tetraoxaspiro-[5,5]undecane) and a 70 30 mole ratio of trans-cyclohexane dimethanol and 1,6-hexanediol after 10 weeks in rabbit. Rods contain 30 wt% levonorgestrel and 2 wt% calcium lactate. (From Ref. 30.)... 

FIGURE 21 Scanning electron micrographs of crosslinked polymer prepared from a 3,9-bis(ethylidene-2,4,8,10-tetraoxaspiro[5,5]un-decane)/3-methyl-l,5-pentanediol prepolymer crosslinked with 1,2,6-hexane triol. Prepolymer contains 1 mol% copolymerized 9,10-dihydroxys tearic acid. Polymer rods, 2.4 x 20 mm, containing 30 wt% levonorgestrel and 7.1 mol% Mg(OH)2. Devices implanted subcutaneously in rabbits, (a) after 6 weeks, 30x (b) after 9 weeks, 30x (c) after 12 weeks, 25x (d) after 16 weeks, 25x. (From Ref. 18.)... 

The next two examples illustrate more complex surface reaction chemistry that brings about the covalent immobilization of bioactive species such as enzymes and catecholamines. Poly [bis (phenoxy)-phosphazene] (compound 1 ) can be used to coat particles of porous alumina with a high-surface-area film of the polymer (23). A scanning electron micrograph of the surface of a coated particle is shown in Fig. 3. The polymer surface is then nitrated and the arylnitro groups reduced to arylamino units. These then provided reactive sites for the immobilization of enzymes, as shown in Scheme III. 

FIG. 9 Confocal laser scanning micrograph of a hollow polymer capsule. The polymer capsule was obtained from polymer multilayer-templated FDA microcrystals after removal of the colloidal core. The FDA microcrystals were coated with SDS and 11 polyelectrolyte layers [(PAH/PSS)3/PAH/ (PSS/PAH-FITC)2]. (PAH-FITC = PAH labeled with fluorescein isothiocyanate.) The microcrystal core was removed by exposure of the coated microcrystals to ethanol, causing solubilization of FDA. 

FIG. 10 SEM micrographs of (a) sUica nanoparticle/polymer [Si02/PDADMAC)3]-coated PS lat-ices and (b) hollow silica capsules. The hollow sUica capsules were obtained by calcining coated particles as shown in (a). The calcination process removes the PS core and the polymer bridging the silica nanoparticles, while at the same time fusing the silica nanoparticles together. Some of the silica capsules were deliberately broken to demonstrate that they were hollow (b). (From Ref. 106.)... 

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