Preparation of a P(THF-co-PO)-b-PB-b-P(THF-co-PO) triblock copolymer via cationic ring-opening polymerization and its use as a thermoset polymer

Abstract

The triblock copolymer poly(tetrahydrofuran-co-propylene oxide)-b-polybutadiene-b-poly(tetrahydrofuran-co-propylene oxide) [P(THF-co-PO)-b-PB-b-P(THF-co-PO)] was synthesized via the cationic ring-opening copolymerization of tetrahydrofuran (THF) and propylene oxide (PO) in the presence of hydroxyl-terminated polybutadiene (HTPB). The copolymerization mechanism was studied using Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance (NMR), and size-exclusion chromatography coupled with multi-angle laser light scattering (SEC-MALLS). The results showed both active chain end (ACE) and activated monomer (AM) mechanisms contribute to the chain propagation process to different extents, and the copolyether segments in triblock copolymer had a gradient microstructure accordingly. Differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and viscosity testing results showed that the triblock copolymer had lower Tg than HTPB, low crystallization tendency and viscosity, and excellent thermal stability. To explore its potential applications, the triblock copolymer was used to prepare elastomer by thermosetting process. Dynamic thermomechanical analysis (DMA) and tensile test results indicated that the triblock copolymer based elastomer had lower Tg, as well as dramatically higher tan δ value and elongation at break, than HTPB based elastomer because of the introduction of copolyether segments.

Using Redox‐Switchable Polymerization Catalysis to Synthesize a Chemically Recyclable Thermoplastic Elastomer

“…These results indicated that poly(THF) formation required an epoxide as a comonomer, a relatively common occurrence for THF polymerization. [42,43,59,60] To avoid gelation, we next explored CHO/THF copolymerization reactions in CH 2 Cl 2 (Table 1, Table S1). A reaction run with an excess of CHO consumed both monomers efficiently (solid lines, Figure 1), and resulted in a moderate molecular weight polyether (M n = Table 1: Molecular weight and composition of THF/CHO copolymers synthesized with various feed ratios, solvents, and concentrations.…”

“…We identified poly(tetrahydrofuran) (poly(THF)) as a potentially useful mid-block for a TPE because it is a flexible polyether with high abrasion resistance. [42][43][44][45][46] It has a glass-transition temperature (T g ) of À 83 °C, [47] making it a useful soft block in segmented polyurethane TPEs like Spandex. [48] While it has a T m of 41 °C, not ideal for a TPE soft block, we envisioned that the crystallinity could be largely disrupted by incorporating a small amount of a comonomer.…”

“…Inspired by research from Hillmyer and co‐workers, who synthesized triblock copolymers that were useful TPEs [37–41] featuring semicrystalline PLLA end‐blocks and flexible biobased polyester mid‐blocks, we targeted the synthesis of TPEs that contained PLLA end‐blocks using our redox‐switchable polymerization strategy. We identified poly(tetrahydrofuran) (poly(THF)) as a potentially useful mid‐block for a TPE because it is a flexible polyether with high abrasion resistance [42–46] . It has a glass‐transition temperature ( T g ) of −83 °C, [47] making it a useful soft block in segmented polyurethane TPEs like Spandex [48] .…”

Hydroxyl Terminated Polybutadiene: Chemical Modification and Application of these Modifiers in Propellants and Explosives

“…Polytetrahydrofuran, with a large number of polar ether bonds, has good cryogenic properties and it is also used to prepared copolymers in order to improve mechanical properties. A novel triblock copolymer poly(tetrahydrofuran-copropylene oxide)-b-polybutadiene-b-poly(tetrahydrofuran-co-propylene oxide) [P(THF-co-PO)-b-PB-b-P(THF-co-PO)] was reported by Fan et al [133,134]. P(THF-co-PO)-b-PB-b-P(THF-co-PO) was synthesized by covalently attaching copolyether segments onto the terminals of HTPB via cationic ring-opening copolymerization of THF and propylene oxide (PO) in the presence of HTPB as a macroinitiator and BF 3 •OEt 2 .…”

Influence of mono-lithium based initiators with different steric volumes on 1,4 unit content of hydroxyl terminated polybutadiene using anionic polymerization

“…1,2 Recently, an important development was reported of the application of HTPB in the eld of solid rocket propellants. [3][4][5][6][7][8][9][10][11][12] Usually, three different segment structures in the HTPB backbone are detected; they are cis-1,4 unit, trans-1,4 unit and 1,2 unit as shown in Scheme 1. Due to these structures, different physical and mechanical properties can be observed.…”