Polarized optical microscopy copolymer

Except for the structure containing 100% of ferrocene unit, which decomposed before melting, all the organometallic copolymers exhibited birefringent melts. Nematic textures were identified by means of polarized optical microscopy and, in one case, by X-ray diffraction studies. For comparison purposes, a polymer without ferrocene unit was prepared, but showed no mesomorphism. The authors deduced that the ferrocene framework was contributing to the liquid crystallinity of the ferrocene-containing polymers. 

The aggregation behavior of selected dibiock copolymers with various compositions was investigated applying several techniques, such as polarized optical microscopy (POM), tensiometry measurements, fluorescence studies, deuterium NMR spectroscopy, SAXS measurements, and cryogenic TEM [4, 5]. In systematic studies we particularly focused on the effect of an increase in the dimethylsiloxane chain length on the aggregation behavior of the investigated surfactants. 

In the literature many differences can be found in the temperature range used for the study of the crystalUzation and melting processes of PEO and PCL based AB diblock and ABA triblock copolymers. When the studies are performed above room temperature, an important fraction of the blocks may remain amorphous [8-11, 14, 16] however, most authors report that when the study is extended at temperatures below Tg, both blocks can crystallize [13-15,17]. In the case of ABA triblock copolymers, it has been found that the B-block remains amorphous when its content is lower than 10%, or its molecular weight is very low. Piao et al. [17] and He et al. [18,19] synthesized either poly(e-caprolactone)-6-poly(ethylene oxide)-6-poly(e-caprolactone) ABA triblock copolymers, as well as poly(ethylene oxide)-6-poly(e-caprolactone) AB diblock copolymers. They used poly(ethylene glycol) (PEG) as precursor and a calcium catalyst. Then, they characterized the materials by using NMR, DSC, WAXS and Polarized Optical Microscopy (POM). Cooling DSC scans carried out by He et al. [18] in AB diblock copolymers of different compositions are presented in Fig. 13.1. 

With increasing neat PVAc content, the heat of fusion decreases and die melting peaks shift to lower temperature in PLA/PVAc blends. The interaction parameters exhibit negative values for up to 10% hydrolyzed PVAc copolymer, but the values increase to positive ones with increasing the degree of hydrolysis. SAXS analysis and polarized optical microscopy observation indicate that a considerable amoimt of PVAc components is located in the interlamellar region. But P(VAc-co-VA) component is expelled out of the interfibrillar regions of the PLA spherulites in PLA/P (VAc-co-VA) blends. 

Polarizing optical microscopy has been used to observe liquid-crystal-like textures of block copolymers which can be particularly distinctive when systems are swollen with solvent. It has also been used to study birefringence and hence to provide a measurement of chain orientation. Information on chain conformation has been obtained from IR and Raman spectroscopy. " ... 

In another study, banded spherulites of PHBV random copolymer were prepared by isothermal crystallization at 90 C for ten hours.Using tapping-mode AFM, the concentric periodic ridges and valleys on the surface of the banded spherulites of this polymer were found to consist of edge-on and flat-on lamellae, respectively. The periodic concentric ridges and valleys observed by AFM corresponded to the periodic extinction rings observed by polarized optical microscopy. AFM measurements showed that the interaction between the AFM probe and the sample surface can be significantly influenced by lamellar orientation. ... 

Light microscopy has been used in a number of contexts to characterize block copolymer morphology. For crystalline block copolymers, spherulitic structures that result from organization of crystalline lamellae can be examined using microscopy. In solutions, polarized light microscopy can reveal the presence of lamellar and hexagonal-packed cylindrical micellar phases. Cubic micellar phases are optically isotropic, and consequently cannot be distinguished from sols only on the basis of microscopy. 

Freeze-fracture reveals intravesicular details in three dimensions. Samples are frozen rapidly in liquid nitrogen and fractured to reveal internal structure. Additionally, lyotropic behavior of amphiphilic ABA triblock copolymers in water has been investigated using polarized light optical microscopy and freeze-fracture TEM [188],... 

Fig. 5.47 A polarized light micrograph (A) of a polyester-nylon copol)nner shows bright and dark bands obscuring the spherulitic texture. Phase contrast optical microscopy (B) reveals the dispersed phase texture of the copolymer which consists of multiple phases where the dispersed phase particles contain subinclusions of the matrix polymer.

The authors also reported on the supramolecular self-assembly from rod—coil—rod triblock copolymers prepared by copolymerization of 5-acetyl-2-aminob-ezophenone with diacetyl functionalized polystyrene with low polydispersity (Scheme 12).110 In contrast to the rod—coil diblock copolymers which exhibit multiple morphologies, the triblock copolymers were found to spontaneously form only microcapsules or spherical vesicles in solution as evidenced by optical polarized, fluorescence optical, and scanning electron microscopies (Figure 33). 

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