  Using molecular dynamics simulations, we provide chain-level insights into
the dissimilarities in rearrangements of polymers under uniaxial tensile and
compressive deformation in glassy and semicrystalline samples of varying chain
lengths. The organization of polymers under tension and compression is
distinctively different. The chains align themselves along the tensile axis
leading to a net global nematic ordering of their bonds and end-to-end vectors
whereas under compression, the polymers arrange themselves in a plane
perpendicular to the compressive axis resulting in emergence of an anti-nematic
ordering of the bonds and the chain end-to-end vectors. Moreover, the degree of
polymers unfolding is greater under tension and they deform less affinely when
compared to chains under compression. The difference between the two responses
strongly depends on the chain length and is the largest at intermediate chain
lengths.
