wileyonlinelibrary.com 1 Full Paper © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Macromolecular Materials and Engineering DOI: 10.1002/mame.201600186 Segmental polyurethanes (PU) with hydrophilic segments form colloidal dispersions which are ultimately arrested into gel-like structure in aqueous continuous phase owing to the dif- ferential interactions between polymer and solvent. These structural states of amphiphilic PUs evolve hierarchically, but the structure-function correlation between PU colloidal disper- sion and gels is not clear. Here, this correlation is defined from the mechanomorphology of hydrophilic polyethylene glycol based PU which forms dispersions and finally transforms into gel-structure. Morphological and rheological analyses show that PU with comparable hydrophilic and hydrophobic con- tent forms attractive colloids with self-similar fractal micro- structures whereas PU with increased hydrophilic character forms space-filling colloids without any defined organiza- tion. Furthermore, colloidal dispersions are densified under shear or gravity to form gel where gel mechanics is defined by colloidal particle organization and the morphology is dependent on gelation mode. This stepwise organization of PU colloidal particles into microgel can independently con- trol microgel mechanics and morphology. Mechano-Morphological Characterization of Polyethylene-Glycol Based Polyurethane Microgel Ayesha Arzumand, Shruti Srinivas, Yuan Yuan, Chi Zhou, Debanjan Sarkar* A. Arzumand, S. Srinivas, Y. Yuan, Prof. D. Sarkar Department of Biomedical Engineering University at Buffalo The State University of New York Buffalo, NY 14260, USA E-mail: debanjan@buffalo.edu Prof. C. Zhou Department of Industrial and Systems Engineering University at Buffalo The State University of New York Buffalo, NY 14260, USA Prof. D. Sarkar Department of Chemical and Biological Engineering University at Buffalo The State University of New York Buffalo, NY 14260, USA where water-swollen PU colloidal particles are dispersed uniformly in the continuous liquid phase due to their ability to assemble into distinct structure. [1] Aggregation of these colloidal particles through coalescence or floc- culation leads to microgel by arresting the particles into space-filling structures. In contrast to conventional col- loidal gel, microgels are defined by colloidal particles which are swollen in good solvent. Transition of molecular PUs into colloidal dispersion and the subsequent aggrega- tion into gel-like solid structure involves complex interac- tions between the polymer and solvent. Both interparticle and particle-solvent interactions define the dispersion of PU colloids which ultimately transform into gel. This hier- archical microstructural evolution of hydrophilic PUs into microgel involves different states of colloids and is regu- lated by PU structure, polymer content, solvent, and envi- ronmental state (e.g., pH, ionic strength, temperature). Thus, it is important to understand and control this tran- sition process where different kinds of interactions are involved at different level. Elucidating the mechanisms 1. Introduction Segmental polyurethanes (PU) designed from hydro- philic segments can form dispersion in aqueous media Early View Publication; these are NOT the final page numbers, use DOI for citation !! Macromol. Mater. Eng. 2016, DOI: 10.1002/mame.201600186