An interesting order-order transition between two different complex nanostructures was observed in a new liquid crystalline linear coil-coil-rod ABC triblock copolymer (triBCP). First

the ABC triBCP

poly(dimethylsiloxane)-

b

-polystyrene-

b

-poly{2

5-bis[(4-methoxyphenyl)oxycarbonyl]styrene} (PDMS-

b

-PS-

b

-PMPCS)

was synthesized through sequential atom transfer radical polymerization. The degrees of polymerization of PDMS

PS

and PMPCS blocks are 58

159

and 106

and the corresponding volume fractions of PDMS

PS

and PMPCS are 0.09

0.29

and 0.62

respectively. The phase behaviors of the PDMS-

b

-PS diblock copolymer precursor and the final triblock copolymer were studied by small-angle X-ray scattering

one-dimensional wide-angle X-ray scattering

and transmission electron microscopy experiments. The PDMS-

b

-PS precursor self-assembles into hexagonally packed cylinders with a relatively small periodic size after thermal annealing. When the triblock copolymer is annealed at a relatively low temperature (120 ℃) at which the PMPCS block is in the amorphous state

the triBCP forms core-shell hexagonally packed cylinders (CSH) with a relativly large periodic size. After the triBCP is annealed above 140 ℃ at which the PMPCS block transforms to the liquid crystalline (LC) phase

the nanophase-separated structure transforms to a three-phase four-layer lamellar structure (LAM-3P4L). Thus

accompanied with the transition of the PMPCS blocks from the amorphous state to the LC phase

the order-order transition from CSH to LAM-3P4L occurs in the PDMS-

b

-PS-

b

-PMPCS ABC triBCP.