Shifting Isotropic-Nematic Transition in Strongly Confined Semi-Flexible Polymer Solutions

We investigated the phase behavior of semi-flexible polymer solutions under sub-persistence length slit confinement of height H.  Strong confinement leads to increased intra-polymer segmental correlation length (l_//) in the unconfined dimensions that could reach up to twice the polymer persistence length P.  The increased l_// results in better alignment of segments and shifts the isotropic-nematic transition density f_IN.  We found that in unconfined systems (H >> P), the dependence of f_IN on P follows Onsager theory predictions. Enhanced segmental alignment is also observed near walls. For strongly confined polymer solutions, f_IN decreases as H decreases due to the increased segmental correlation length, and enhanced segmental alignment is found throughout the solution.  Qualitative agreements with mean-field theory are found.  The shift in f_IN also affects the confined polymer solution dynamics.