Self Assembly in Functionalized Butadiene Based Polyurethanes Konda Reddy Kunduru, Billa Narasimha Rao, and Tushar Jana* Chemical modification of hydroxyl terminated polybutadiene (HTPB) oligomer without altering its inherent properties is achieved by covalently attaching various functional moieties such as 2, 4-dinitrophenyl (DNB) and triazine derivatives to the terminal carbons of HTPB. Fibrous self-assembly network formed by the hydrogen bonding through DNB groups is found to be the driving force for the unprecedented simultaneous improvement in both tensile strength and elongation in case of HTPB-DNB based polyurethane (PU). For example, tensile strength and elongation at break of the PU obtained using isophorone diisocyanate are found to be 1.21 MPa and 570.26%, respectively in case of HTPB-DNB whereas these values are 0.36 MPa and 91.22%, respectively in case of HTPB. In contrary, non hydrogen bonding supramolecular assembly of hard segment domains in triazine functionalized HTPB-PU resulted in reinforcement of mechanical strength and aggregation induced emission. 1. Introduction Hydroxyl terminated polybutadiene (HTPB) is a viscous liquid rubber consisting of terminal hydroxyl groups and is widely used as binder in solid rocket propellants owing to its high tensile and tear strength, good thermal, and chemical resistance. [1] Polyur- ethanes (PUs) prepared from HTPB showed enormous applications as adhesives, sealants, membranes, coatings, etc. [1] Understanding of the structure property relationships in PUs [2,3] especially in case of segmented PUs, which are formed due to the incompatibility of hard and soft segments of PUs, are of a great interests since varieties of domain structure can be achieved because of phase segregation. Most of the HTPB based PUs reported in the literature were studied for their structure- property relationships in terms of mechanical and thermal stability studies. [4–6] Also efforts have been put to understand the diisocyante structure on the structure-property phenomena. [7,8] It was also understood from the literature that most of the studies have tried to improve the tensile properties of the HTPB based PUs. Chemical modification has been also used as a strategy to improve the mechanical properties of PUs. In this article, we compare the structure- property relationships of terminally functionalized HTPB based PUs. For this, we have selected dinitrochlorobenzene (DNCB), cyanuric chloride (CYC), 2- chloro-4, 6-bis (dimethylamino)-1, 3, 5- triazine (CBDT), 1-chloro3, 5-diazido-2, 4, 6- triazine (CDT) to modify the HTPB backbone by attaching these functionalities on the terminal carbons of HTPB to obtain terminal functionalization. These four terminally functionalized HTPB molecules contain aromatic and heterocyclic aromatic rings having different substituents with varying nature. [9–11] Polyurethanes were synthesized utilizing these four terminally functionalized HTPB diols with various diisocyanates. The correlations of the properties of the synthesized polyur- ethanes are based on the experimental observations from our previous published articles. [12,13] In these studies, we have compared the influence of terminal functionality on the mechanical properties of the terminally functionalized HTPB PUs. To understand the cause, we evaluated and compared structural and morphological behavior of all the PUs. All these properties in terms of their result compared with the pristine HTPB-PU prepared and studied under similar conditions. 2. Experimental Section Synthesis of functionalized HTPB with dinitrochlorobenzene (DNCB), cyanuric chloride (CYC), 2-chloro-4, 6-bis (dimethyla- mino)-1, 3, 5-triazine (CBDT), 1-chloro3, 5-diazido-2, 4, 6- triazine (CDT), [9–11] and their respective polyurethanes have been reported and discussed in details in our previous works. [12,13] The chemical structure of modified HTPB-PU backbone is shown in Scheme 1. 3. Results and Discussion 3.1. Synthesis and Spectroscopic Conformation of Functionalized HTPB Based PUs Pristine HTPB and functionalized HTPB (HTPB-DNB, HTPB- CYC, HTPB-CBDT, and HTPB-DT) have been utilized to synthesize polyurethanes (PUs) and characterized by various spectroscopic methods. All the PUs have been prepared by the K. R. Kunduru, B. N. Rao, T. Jana School of Chemistry University of Hyderabad Hyderabad, India E-mail: tusharjana@uohyd.ac.in DOI: 10.1002/masy.201800090 Macromolecular Symposia Polyurethane www.ms-journal.de FULL PAPER Macromol. Symp. 2018, 382, 1800090 © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 1800090 (1 of 6)