β-Myrcene/isobornyl methacrylate SG1 nitroxide-mediated controlled radical polymerization: synthesis and characterization of gradient, diblock and triblock copolymers.

Adrien Métafiot,Brigitte Defoort,Pascal Hubert,Sébastien Pruvost,Jean-François Gérard,Milan Marić,Lysandre Gagnon

doi:10.1039/c8ra09192g

Abstract

β-Myrcene (My), a natural 1,3-diene, and isobornyl methacrylate (IBOMA), from partially bio-based raw materials sources, were copolymerized by nitroxide-mediated polymerization (NMP) in bulk using the SG1-based BlocBuilder™ alkoxyamine functionalized with an N-succinimidyl ester group, NHS-BlocBuilder, at T = 100 °C with initial IBOMA molar feed compositions fIBOMA,0 = 0.10–0.90. Copolymer reactivity ratios were rMy = 1.90–2.16 and rIBOMA = 0.02–0.07 using Fineman–Ross, Kelen–Tudos and non-linear least-squares fitting to the Mayo–Lewis terminal model and indicated the possibility of gradient My/IBOMA copolymers. A linear increase in molecular weight versus conversion and a low dispersity (Đ ≤ 1.41) were exhibited by My/IBOMA copolymerization with fIBOMA,0 ≤ 0.80. My-rich and IBOMA-rich copolymers were shown to have a high degree of chain-end fidelity by performing subsequent chain-extensions with IBOMA and/or My, and by 31P NMR analysis. The preparation by NMP of My/IBOMA thermoplastic elastomers (TPEs), mostly bio-sourced, was then attempted. IBOMA-My-IBOMA triblock copolymers containing a minor fraction of My or styrene (S) units in the outer hard segments (Mn = 51–95 kg mol−1, Đ = 1.91–2.23 and FIBOMA = 0.28–0.36) were synthesized using SG1-terminated poly(ethylene-stat-butylene) dialkoxyamine. The micro-phase separation was suggested by the detection of two distinct Tgs at about −60 °C and +180 °C and confirmed by atomic force microscopy (AFM). A plastic stress–strain behavior (stress at break σB = 3.90 ± 0.22 MPa, elongation at break εB = 490 ± 31%) associated to an upper service temperature of about 140 °C were also highlighted for these triblock polymers.

Highlights

The community of polymer researchers has long desired to elaborate on polymerization techniques that couple the control of microstructure offered by living ionic polymerization[1,2,3] with the simplicity of industrial implementation made possible by other processes such as free radical polymerization.[4]
We studied the well-controlled polymerization of b-myrcene,[29] an acyclic monoterpene, initiated by the unimolecular SG1-based succinimidyl ester-functionalized BlocBuilderTM alkoxyamine called NHS-BlocBuilder,[30] demonstrating once again the facility of the nitroxide-mediated polymerization (NMP) process to synthesize elastomers based on 1,3-dienes with low dispersity (Đ) and substantial chain-end delity
My/isobornyl methacrylate (IBOMA) NMP in bulk at 100 C initiated by NHS-BB highlighted the gradient nature of this copolymerization with the higher reactivity of the monoterpene toward both propagating species (/Myc and /IBOMAc) compared of that of the bulky methacrylate

Summary

Introduction

The community of polymer researchers has long desired to elaborate on polymerization techniques that couple the control of microstructure offered by living ionic polymerization[1,2,3] with the simplicity of industrial implementation made possible by other processes such as free radical polymerization.[4]. The development of styrenic-diene block copolymers, generally composed of a dispersed poly(styrene) (PS) or PS derivative phase in a continuous elastomer domain,[14,15] looks speci cally suited to the NMP process. The NMP of conjugated dienes such as butadiene (B)[16,17] and especially isoprene (I)[18] was explored from the onset of the development of NMP, using 2,2,6,6-tetramethylpiperidinyl-1-oxy (TEMPO),[7] the original rst-generation stable free nitroxide. We studied the well-controlled polymerization of b-myrcene,[29] an acyclic monoterpene, initiated by the unimolecular SG1-based succinimidyl ester-functionalized BlocBuilderTM alkoxyamine called NHS-BlocBuilder,[30] demonstrating once again the facility of the NMP process to synthesize elastomers based on 1,3-dienes with low dispersity (Đ) and substantial chain-end delity N-tert-Butyl-N-[1-diethylphosphono-(2,2dimethylpropyl)]nitroxide (SG1)[25] showed its effectiveness to control the polymerization of I.26–28 Recently, we studied the well-controlled polymerization of b-myrcene,[29] an acyclic monoterpene, initiated by the unimolecular SG1-based succinimidyl ester-functionalized BlocBuilderTM alkoxyamine called NHS-BlocBuilder,[30] demonstrating once again the facility of the NMP process to synthesize elastomers based on 1,3-dienes with low dispersity (Đ) and substantial chain-end delity

Methods

Results

Conclusion