Systems and methods for releasably coupling an adjunct material to an end effector for a surgical instrument are provided. The adjunct can be configured to be releasably retained on a jaw, such as a cartridge or anvil, using a contractible attachment feature configured to be transitioned from an original, non-contracted configuration to a contracted configuration under application of heat. The attachment feature, such as one or more strands of a shrinkable polymer, can be engaged with the adjunct, and contraction of the attachment feature is effective to couple the adjunct with retaining members formed on the jaw. Another type of an adjunct has at least one portion configured to be reversibly stretched using application of a force such that, when the force is removed, the portion transitions from a stretched configuration to a contracted configuration and thereby causes the adjunct to be engaged with retaining members formed on the jaw.