Monomers optical microscopy

Fig. 36 Self-assembly of DNA-coated colloids observed in optical microscopy, (a) Fractal-like aggregates of microspheres with 14,000 DNA molecules per each sphere, (b, c) Similar colloids with 3,700 DNA/sphere form small crystals, (d) Upon heating by only 2°C, the crystallites and the aggregates both melt into monomers. Adapted with permission from [153]...

Polarization, and NLO properties, 12, 102 Polarized optical microscopy, metallomesogen mesophase characterization, 12, 208 Polar monomers, polymerization, 1, 147 Polar polyolefins, co-polymerizations, 11, 723 Polyacetylenes... 

The monomers XXIV-m-n were polymerized with initiator 4 in a monomer to initiator ratio of about 50. Table 16 summarizes the physico-chemical data for these polymers. Poly-(XXIV-m-n) exhibited smectic C mesophases, but these phases were only observed over a small temperature range and isotropization occurred shortly after the glass transition. It was not possible to identify the mesophase by polarized optical microscopy, but the smectic phase was confirmed by X-ray scattering experiments. Transition temperatures increased with the length of the carbon segments (n) but decreased with increasing siloxane segment (m). 

Various means of particle identification are possible with optical microscopy. These include dispersion staining for identification of asbestos particles [44] and the use of various mounting media [45], Proctor et. al. [46,47] dispersed particles in a solidifying medium of Perspex monomer and hardener. This was poured into a plastic mold that was slowly rotated to ensure good mixing. Microscope analyses were carried out on thick sections a lower size limit of 5 p,m was due to contamination. 

Some orientation was retained on thermal polymerization of p-benz-amidostyrene when polymerization was carried out below the polymer glass transition temp>erature 66). Again the monomer crystal has a layer structure separating reactive radicals. The reaction proceeded in successive layers of the monomer crystal form the outside to the inside without induction period. However, the retained orientation detected by optical microscopy and infrared dichroism disappeared above the glass transition temperature of the polymer. Again no path to a polymer crystal structure seems to be available in this reaction. The polymer produced is slightly less dense than the monomer crystal since it is amorphous (6K5). Similar orientation in the amorphous state was found on polymerization of terephthalonitril oxide aystals 67). 

Characterization. The liquid crystalline properties of the side-chain monomers (III) and polymers (I) have been studied by Differential Scanning Calorimetry (DSC), Polarized Optical Microscopy (POM) and X-ray diffraction. The thermal transition data and phase types for all monomers (III) and polymers (I) are summarized in Table HI. A representative DSC scan for the monomer (El) and polymer (p with a four-carbon tail (n=4) and six-carbon flexible spacer (m=6) are shown in Figures 1 and 2 respectively. The first peak at -24°C shown in Figure 1 is the crystal to smectic... 

The monomer exhibits complex phase behaviour, in particular, a monotropic liquid crystalline phase, which is only apparent on cooling, such materials can only be properly characterized by using differential scanning calorimetry (DSC) in conjuction with optical microscopy and also by X-ray scattering (see Chapter 1). 

A Nicolet Magna 550 Fourier Transform Infrared Spectrometer (FTIR) and a Bruker MW 250 MHz proton NMR were used to verify the chemical structure of all monomers and polymers. Optical activity of the compounds was measured at 25 on a Perkin-Elmer Polarimeter in chloroform. A Waters Gel Permeation Chromatograph with 440 UV absorption detector and R401 differential refructometer was used to determine the molecular weights of the polymers tetrahydrofuran was used as the mobile phase at 1.0 mL/min, and the Waters polystyrene gel columns were calibrated with monodisperse polystyrene standards. Polarizing optical microscopy was used to identify liquid crystalline phases using a Leitz optical microscope with a CCD camera attachment... 

The optical microscopy of these polymer liquid crystals identifies both polymers as having smectic A phases only. However unlike monomer materials the evolution of a particular well defined texture may take several hours. As is shown in plates l(a-c) the smectic fan texture can be seen to grow gradually over 15 hours on annealing just below All of the photomicrographs are for PG296 which... 

The optical textures of the monomers were characterized by means of hot-stage polarized optical microscopy (POM) some representative optical textures are presented in Fig. 6.1. When PPUB was heated above 84 °C, eyesight became bright and LC textures appeared. Upon heating to 104 C, textures vividly appeared and schlieren textures of SC phase were exposed, as shown in Fig. 6.1(a). Upon heating the sample to 158 °C, a droplet texture of nematic phase appeared (Fig. 6.1(b)). However, the droplet... 

The monomers and polymers were characterized by infrared (IR) and ultraviolet-visible (UV-vis) spectroscopy, H and - C nuclear magnetic resonance (NMR), element analyses, differential scanning calorimetry (DSC), and polarizing optical microscopy. The molecular weights of the polymers were evaluated by gel permeation chromatography (GPC) using polystyrene standards, and electrical conductivities upon iodine doping for the cast film of the polymers were measured by the four-probe method. 

Molau and Keskkula [351] were among the first to study the mechanism of particle formation in rubber containing polymers. They showed that phase separation occurs between the rubber and a vinyl polymer during the polymerization of solutions of rubber in vinyl monomers which is followed by formation of an oil-in-oil emulsion. During phase inversion of the emulsion, rubber solution droplets are formed which change into solid rubber particles in the final polymer. Structural investigations by phase contrast optical microscopy, shown in this chapter (Section 5.3), reveal dispersed particle size and distribution. Ugelstad and Mork [352] reported on new diffusion methods for the preparation of emulsions and polymer dispersions where the size and distribution of the latex particles were monitored by very simple optical, SEM and TEM methods. A microemulsion polymerization has been reported for the first time [353] with... 

Unlike styrene and acrylic monomers, VCM is a gas at stp and hence suspensions or emulsions of liquid VCM in water at elevated pressures are not very amenable to study by optical microscopy. 

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