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Thiol–ene addition enables tailored synthesis of poly(2‐oxazoline)‐ graft ‐poly(vinyl pyrrolidone) copolymers for binder jetting 3D printing
Author(s) -
Wilts Emily M,
Long Timothy E
Publication year - 2020
Publication title -
polymer international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.592
H-Index - 105
eISSN - 1097-0126
pISSN - 0959-8103
DOI - 10.1002/pi.6074
Subject(s) - polymer chemistry , copolymer , chain transfer , aqueous solution , materials science , lower critical solution temperature , polymerization , chemistry , polymer , organic chemistry , radical polymerization
The continued interest in graft copolymer architectures arises from their unique solution properties and potential for a myriad of applications ranging from drug delivery to adhesives. Poly(vinyl pyrrolidone) (PVP) represents a popular amorphous, water‐soluble polymer used as a polymeric binder in binder jetting additive manufacturing, as fillers in cosmetic products, and for subcutaneous drug delivery systems. This report describes the synthesis of poly(2‐oxazoline) and PVP graft copolymers using a ‘grafting to’ methodology with an efficient thiol–ene ‘click’ reaction. Copolymerization of 2‐methyl‐2‐oxazoline and 2‐(3‐butenyl)‐2‐oxazoline introduced pendent vinyl grafting sites with a predictable absolute number‐average molecular weight. In parallel, reversible addition‐fragmentation chain‐transfer polymerization and subsequent aminolysis yielded well‐defined, oligomeric, thiol‐terminated PVP. Thiol–ene click chemistry enabled the formation of poly(2‐oxazoline)‐ graft ‐poly(vinyl pyrrolidone) (PMeOx‐ g ‐PVP) copolymers with varying mole percent grafting sites and PVP graft length. 1 H NMR spectroscopy, aqueous SEC with multiangle light scattering (SEC‐MALS), and bromine titrations confirmed chemical structure, and DSC with TGA elucidated thermal transitions. Aqueous SEC‐MALS and 1 H NMR spectroscopy also determined absolute number‐ and weight‐average molecular weights and average grafting levels, which revealed optimal reaction conditions. Zero‐shear viscosities of 5 and 10 wt% solutions in deionized water for each graft copolymer compared to their linear analogs demonstrated a significant ( ca 31%) decrease in viscosity at the same number‐average molecular weight. This decrease in solution viscosity suggested PMeOx‐ g ‐PVP copolymers as exceptional alternatives to linear analogs for aqueous‐based, binder jetting additive manufacturing.