The present disclosure provides injectable synthetic and biodegradable polymeric biomaterials that effectively prevent seroma, a common postoperative complication following ablative and reconstructive surgeries. Provided biomaterials include physically crosslinked hydrogels that are thixotropic, display rapid chain relaxation, are easily extruded through narrow gauge needles, biodegrade into inert products, are well tolerated by soft tissues, and effectively prevent seroma in a radical breast mastectomy animal model.