Irradiation lamellar crystal

Mesophases can be locked into a polymer network by making use of polymerizable LCs [59]. These molecules contain moieties such as acryloyl, diacety-lenic, and diene. Self-organization and in situ photopolymerization under UV irradiation will provide ordered nanostmctured polymers maintaining the stable LC order over a wide temperature range. A number of thermotropic liquid crystalline phases, including the nematic and smectic mesophases, have been successfully applied to synthesize polymer networks. Polymerization of reactive lyotropic liquid crystals also have been employed for preparation of nanoporous polymeric materials [58, 60]. For the constmction of nanoporous membranes, lyotropics hexagonal or columnar, lamellar or smectic, and bicontinuous cubic phases have been used, polymerized, and utilized demonstrated in a variety of applications (Fig. 2.11). 

The effect of irradiation on the crystallinity of UHMWPE has already been described. Irradiation of UHMWPE in the melt leads to a high yield of crosslinks with effectively no chain scission occurring, and with increasing crosslink density a change from lamellar to micellar-like crystallization was found [83]. More recent thorough studies of UHMWPE often at sterilizing doses of around 25-50 kGy, show both scission and crosslinking as well as a transition zone within and below the polymer mass [84-87]. 

T> Tg, for irradiation above the melting range, the whole sample exists in the molten (amorphous) state. Cross-linking of macromolecules by irradiation also yields a stabilization of this phase after cooling down to room temperature (i.e., any crystallization is prevented, and no lamellar structures are visible in TEM). 

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