Styrene/alkylacrylate copolymers: Relationship between molecular structure and properties

•St/MA copolymers have stronger “molecular structure/microstructure” dependence.•Gradient and random heterogeneous St/MA copolymers have the same main phase.•Central part in gradient copolymers provides intramolecular compatibility.•Microstructure and Tg of St/tBA copolymers are the same for all types of copolymers.

To investigate the influence of copolymer molecular structure on its properties five copolymer types of styrene (St) with tert-butylactylate (tBA) and St with methylacrylate (MA) were synthesized. Gradient, block-random and diblock-copolymers were obtained via NMP polymerization using SG1 and TEMPO as reversible inhibitors. Random homogeneous and heterogeneous copolymers were synthesized using conventional radical polymerization. Peculiarities of phase separation in these copolymers were investigated by AFM and DSC. Gradient and random heterogeneous St/MA (FSt = 30 mol%) copolymers have heterophase structure with similar main phase (FSt ≈ 45 mol%) that specifies Tg and mechanical properties of entire copolymer. Thus gradient and random heterogeneous have approximately the same tensile strength (25 MPa) and modulus (0.5 GPa), whereas random uniform copolymer behaves like typical rubber (modulus 35 MPa and strain about 600%) since it has Tg = 18 °C. St/tBA copolymers have homogeneous structure with the same Tg = 59 °C independently on chain structure.

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