A Non-Isocyanate Route to Poly(Ether Urethane): Synthesis and Effect of Chemical Structures of Hard Segment

Abstract

A series of non-isocyanate poly(ether urethane) (PEU) were prepared by an environmentally friendly route based on dimethyl carbonate, diols and a polyether. The effect of the chemical structure of polyurethane hard segments on the properties of this kind of PEU was systematically investigated in this work. Polyurethane hard segments with different structures were first prepared from hexamethylene di-carbamate (BHC) and different diols (butanediol, hexanediol, octanediol and decanediol). Subsequently, a series of non-isocyanate PEU were obtained by polycondensation of the polyurethane hard segments with the polyether soft segments (PTMG2000). The PEU were characterized by GPC, FT-IR, 1H NMR, DSC, WAXD, SAXS, AFM and tensile testing. The results show that the urea groups generated by the side reaction affect the degree of crystallization of hard segments by influencing the hydrogen bonding of the hard segments molecular chains. The degree of hard segment crystallization, in turn, affects the thermal and mechanical properties of the polymer. The urea group content is related to the carbon chain length of the diol used for the synthesis of hard segments. When butanediol is applied to synthesize hard segment, the hard segment of the resulting PEU is unable to crystallize. Therefore, the tensile strength and modulus of elasticity of butanediol-based PEU is lowest among three, though it possesses the highest urea group content. When longer octanediol or decanediol is applied to synthesize the hard segment, the hard segments in the resulting polyether-based polyurethane are crystallizable and the resulting PEU possesses higher tensile strength.

Vat Photopolymerization of Nanocellulose-Reinforced Vegetable Oil-Based Resins: Synergy in Morphology and Functionalization

“…When an excess HMDI is added, the urethane groups react with free isocyanate groups. This reaction forms a cross-linked polymer layer on the NCC surface, as evidenced by the intense absorption maximum at 1651 cm –1 assigned to the carbonyl on the urea group . The NCO peak also confirms the introduction of diisocyanate at 2264 cm –1 as well as characteristic peaks at 1440, 2857, and 2933 cm –1 assigned to CH bending vibrations and symmetric and antisymmetric CH 2 vibrations, respectively. ,, The peak at 2890 cm –1 , which overlaps with peaks at 2857 and 2933 cm –1 , is related to the CH stretching in the cellulose molecule .…”

Cyclic carbonates as building blocks for non‐isocyanate polyurethanes

“…The increased amount of urea groups compared to NIPU‐EC could be due to different interaction capability of polymer chains. In NIPU‐PC the pendant methyl group could disturb hydrogen bonding or crystallization capability of hard segments, which is known to reduce urea groups 34,35 . Another possible reason could be the reactivity differences for cyclic carbonate, where the amine originating from back biting reaction more readily attacks the NIPU polymer instead of the cyclic carbonate to reform DHU.…”

Non-Isocyanate Aliphatic–Aromatic Poly(carbonate-urethane)s—An Insight into Transurethanization Reactions and Structure–Property Relationships

“…NIPCU_1_5 demonstrated a high tensile strength of 40 MPa and an elongation at break of 130%, whereas NIPCU_1_6 and NIPCU_1_10 containing longer alkyl chains in their hard segments displayed tensile strengths of 37 MPa and 18 MPa, and elongations at break of 300 and 550%, respectively. Thanks to both their toughness and flexibility, they are attractive alternatives for known NIPUs [ 6 , 19 , 22 , 37 , 38 ].…”

“…The type of α,ω-diol, used during transurethanization with BMC, affects the reaction process, determines the possible occurrence of side reactions, and defines the structure of hard segments and properties of the NIPUs [ 6 , 19 , 32 , 38 ]. On one hand, the application of shorter α,ω-diol (e.g., 1,2-ethanediol) facilitates the further diffusion of low-molar-mass products during transurethane polycondensation due to its lower boiling point.…”

“…However, the presence of 2-hydroethyl carbamate moieties accelerates the formation of urea groups via back-biting side reactions [ 6 , 31 , 32 ]. The increase in the chain length of α,ω-diol decreases the tendency to form urea groups [ 38 ].…”