Synthesis and Analysis of Well-Defined Copolymers via by Combination ROP Technique

Herein, the poly(ɛ-caprolactone)-poly(ethylene glycol)-poly(ɛ-caprolactone) (PCL-PEG-PCL) macro xanthate reversible addition–fragmentation chain-transfer agent is obtained on the polyethylene glycol (PEG) (600, 1000, and 1500 g mol⁻¹) block, after the addition of ɛ-caprolactone via ring-opening polymerization. Then, poly (styrene-b-ɛ-caprolactone-b-PEG-b-ɛ-caprolactone-b-styrene) pentablock copolymer is synthesized reversible addition–fragmentation chain-transfer (RAFT) solution polymerization technique via mediated PCL-PEG-PCL xanthate macro-RAFT agents and 2,2′-azobisisobutyronitrile as initiator. The products are demonstrated using Fourier transform infrared spectrophotometer (FT-IR), proton nuclear magnetic resonance (¹H-NMR), carbon nuclear magnetic resonance (¹³C-NMR), differential scanning calorimetry (DSC), and gel permeation chromatography (GPC) analyses. First-order linear kinetic graphs of the reaction mechanism are observed with an increase in molecular weights (M_W) between 16 000 and 36 000 g mol⁻¹. The narrow dispersity (Đ = 1.40–1.48) polymer formation of styrene (St) controlled by RAFT polymerization confirms the increase in molecular weight according to the polymerization time. The reaction kinetics are first order and the rate constants are found to be k₁ = 6.16 × 10⁻⁴s⁻¹, k₂ = 6.91 × 10⁻⁴ s⁻¹ and k₃ = 7.33 × 10⁻⁴ s⁻¹. Thermal and spectroscopic analyses prove that the reactions are carried out successfully.