Tunning switch temperature of shape memory polyacrylamide hydrogel

Sonia Norouzi Esfahany; Mehrdad Kokabi; Ghazaleh Alamdarnejad

Tunning switch temperature of shape memory polyacrylamide hydrogel

8^th International Conference on Smart Materials and Structures
August 01-02, 2019 Dublin, Ireland

Sonia Norouzi Esfahany, Mehrdad Kokabi and Ghazaleh Alamdarnejad

Tarbiat Modares University, Iran

Posters & Accepted Abstracts: Nano Res Appl

Abstract

In this work, chemically cross-linked polyacrylamide (PAAm) hydrogel prepared by free radical polymeriztion. The effect of water content on glass tarnsition temperature (Tg) of hydrogel, as switch temperature of shape memory system, was investigated using dynamic mechanical analysis (DMA). The transition temperature, i.e. the desired switch temperature for our work, was chosen around ~ 30oC by tunning the water content of hydrogel at 25%, Fig. 1. Shape memory behaviour of chosen hydrogel was investigated for a full cycle, i.e. four steps, by DMA. The four steps procedure performed at a constant heating/cooling rate of 5oC.min-1. First, the sample was heated to 50oC (above the switch temperature) and stretched to a certain strain (ε) under a constant force (Step 1). Then, the deformed sample was cooled to -50oC under the fixed force (Step 2). The force then removed and the temporary strain was measured (Step 3). Finally, the sample was reheated to 50oC and kept for 50 min in this temperature, then the recovery strain recorded (Step 4). The shape fixing ratio and shape recovery ratio as the main characteristics of shape memory polymeric system calculated from Fig. 2. The results indicated that the shape fixing ratio and shape recovery ratio of the system were 96% and 78%, respectively. Recovering to orginal shape was started around 10oC. The sample showed good shape fixity because of existence the hydrogen bonds between PAAm and water. Hydrogen bonds as physical cross linkers could improve structural strength of the sample.