Development of self-healing polymer composites and photoinduced ring-opening metathesis polymerization

The design and development of “smart-materials” which are capable of assessing their internal damage and perform self-healing is described. Failure of a material occurs by the induction of cracks. Often cracks are formed deep within the structure where detection is difficult and repair is virtually impossible. Once cracks have formed within polymeric materials, the integrity of the structure is compromised. A composite material can be repaired and its lifetime enhanced by relieving stress concentrations surrounding the crack tip.; This thesis reports the novel development of a structural polymeric material with the ability to self-heal cracks by the application of ring opening metathesis polymerization. Self-healing is accomplished by incorporating a microencapsulated healing agent and a catalytic chemical trigger within an epoxy matrix. When the material is damaged, the microcapsules rupture and release the healing agent into the damaged region through capillary action. As the healing agent contacts the catalyst, polymerization is initiated and the damage is repaired. Ring opening metathesis polymerization (ROMP) has been applied towards the development of a self-healing polymer composite. Grubbs' catalyst is embedded in the matrix as a solid and dicyclopentadiene is employed as the healing agent within the microcapsules. Chemical and micromechanical experiments have been performed that illustrate the ROMP based self-healing concept. Experiments on fracture specimens have yielded as much as 75% recovery of virgin toughness.; In addition, the development and utility of these easily accessible ruthenium precatalyst, [(p-cymene)RuCl₂]₂ and tricyclohexylphosphine in performing Photoinduced Ring Opening Metathesis Polymerization (PROMP) is demonstrated. Polymerization of norbornene and dicyclopentadiene has been performed, showing the simplicity and ease of this procedure. The resulting poly(norbornene) shows high trans content (85%) of the ring opened double bonds. Crosslinked poly(dicyclopentadiene) can be generated at room temperature using 1% wt. of the precatalyst by irradiation of UV light at 254 nm. Initial results in the application of PROMP towards photopatterning and creation of microchannels for potential application in microfluidic devices is described.