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Toward Smart Materials: Self-healing Polymers

The research is focused on adding biologically inspired self-healing features to polymers with various properties such as low glass transition temperature, high glass transition temperature, hydrophobic, water soluble, amorphous and semi crystalline.

The envisaged self-healing classic mechanism implies the dispersion of microcapsules (polyureaformaldehyde) filled with monomer (dicyclopentadiene) and of catalyst within resins. The self-healing is triggered by local stresses that initiate the rupture of microcapsules and the release of the monomer.

Self-healing block copolymers (polystyrene-block-polyisoprene block-polystyrene) were obtained by dissolving the polymer in a solvent that does not dissolve the micro bubbles and does not deactivate the Grubbs catalyst.

The research will ignite for the first time detailed studies on the effect of the added self-healing capabilities on the behavior of self-healing polymers and a thorough analysis of the lifetime of added self-healing features to various polymers.

The results obtained are promising and were published in Polymer for Advanced Technologies (M. D. Chipara, M. Chipara E. Shansky, J. Zaleski, Self - Healing o fHigh Elasticity Block Copolymers, 2009).

Polymers

Figure 1: Microscopy pictures of polymeric micro-bubbles. (A: Optical Microscopy. B-E: SEM pictures)

Figure 2: Stress & strain dependencies for polystyrene-block-polyisoprene-block-polystyrene filled with 5 % microcapsules containing DCPD (black line; self-healing features not activated) and polystyrene-block-polyisoprene block-polystyrene filled with 5 % microbubbles containing DCPD and loaded with 1 % Grubbs catalyst.

Figure 3: Raman spectra of type II sample after sample's fracture, from bottom to top:
Line 1: Before fracture
Line 2: 10 minutes after fracture
Line 3: 30 minutes after fracture
Line 4: 8 hours after fracture.

Instrumentation

The laboratory is equipped with fume hood, stirring plates, hot plates, digital stirring plate, mechanical testing equipment (Testresources R 1100), spin-coater, sonicator, pH meter and glassware for the synthesis of the microcapsules filled with DCPD.

Also, in the Physics and Geology Department we have available a Bruker Discovery X-Ray Spectrometer. In addition, a wide range of high performance spectrometers are available within the College of Science and Engineering such as Bruker Senterra Raman spectrometer operating at 785 nm (equipped with a high performance fiber optic probe), , TA Instruments (Q100) Differential Scanning Calorimeter, and various FTIR, UV-VIS, and fluorescence spectrometers.