Radical‐Regulated Synthesis of Long‐Chain Branched Polylactic Acid Toward Enhanced Melt Strength

ABSTRACT In this work, long‐chain branched polylactic acid (LCB‐PLA) with enhanced melt strength was synthesized via a radical‐regulated strategy using diisopropylphenyl peroxide (DCP) as the radical initiator, polyfunctional pentaerythritol tetraacrylate (PET4A) as the branching agent, and tetramethyltoluene disulfide (TMTD) as the radical regulators. Meanwhile, the synthesized mechanism of the functional PLA was investigated. Experimental results demonstrated that TMTD effectively promoted the branching efficiency of PET4A monomers and facilitated the formation of long branched chains along the PLA backbone. Moreover, the terminal slope of the storage modulus for the modified PLA decreased from 1.76 to 0.74. Additionally, deviations observed in the Cole–Cole plot indicated slower molecular chain relaxation after long‐chain branching, along with prolonged relaxation time. Notably, the crystallinity, crystallization rate, and crystallization temperature of the modified PLA all improved with increasing branching degree, with the half‐crystallization time reduced to 0.47 min. Thus, the modified PLA synthesized via this radical‐regulated strategy exhibited significantly enhanced melt strength and improved crystallization behavior, which may broaden its applicability in processing‐related applications.