A variety of thermoresponsive materials are based on the temperature-induced collapse of macromolecules in solutions. One of the most common polymers used in these applications is poly(N-isopropylacrylamide) (PNIPAM). Aqueous solutions of PNIPAM present a lower critical solution temperature transition (LCST). At low temperatures the polymer is water-soluble and adopts an extended configuration while at higher temperatures (>305K) a reversible transition occurs during which the polymer collapses to a globule. Detailed molecular information on the structure of dilute PNIPAM chains and the temperature-induced changes has been limited due to significant difficulties present in experimental studies (i.e. interchain aggregation and polydispersity). In the present study, atomistic simulations of poly(N-isopropylacrylamide) oligomers aim at exploring the molecular characteristics of aqueous solutions in full atomistic detail at low molecular weights. By considering an atomistic PNIPAM model in explicit solvent the effect of temperature induced-changes as a function of molecular architecture (tacticity) is explored. The water organization and hydrogen-bonding is analyzed and results are consistent with a hydrophilic behavior at low temperatures and low molecular weights. The analysis of the local structure of the polymer molecules provides important information for further studies using a coarse-grain description.