Synthesis and Structure–Property Relationship of Amphiphilic Poly(2-ethyl-co-2-(alkyl/aryl)-2-oxazoline) Copolymers

Abstract

Poly(2-oxazoline)s (POZs) are widely investigated for their applications in various fields due to their unique properties. To exploit and combine different characteristics of the POZ family, 2-oxazoline monomers can be copolymerized to prepare tailor-made copolymers with the desired glass transition temperature (T g), melting temperature (T m), amphiphilicity, and functionality. Here, we report the synthesis and characterization of 2-oxazoline monomers and a range of POZ copolymers produced, thereof. 2-Propyl-2-oxazoline (PrOZ) and 2-pentyl-2-oxazoline (PeOZ) monomers were synthesized by two different methods starting from nitriles or carboxylic acids. A number of POZ copolymers were synthesized by copolymerization of 2-ethyl-2-oxazoline (EOZ) with either one of PrOZ, PeOZ, or 2-phenyl-2-oxazoline (PhOZ) at three different compositions (25:75, 50:50, and 75:25) and three molecular weights (1000, 2000, and 5000 Da). The successful synthesis of the monomers and copolymers was demonstrated through their structural analysis by 1H NMR and FTIR. SEC results confirmed the targeted molar masses of the copolymers and living nature of the polymerization by showing low dispersity values. Thermal properties of the copolymers were studied using DSC and TGA. DSC studies revealed the amorph and random state of the copolymers with obtained T g values for the copolymers in the range of −3 to 84 °C depending on their molecular weight and type of the side chain. While the presence of longer aliphatic side chains resulted in lower T g values, the presence of 2-phenyl substituents on the polymer led to higher T g values. The decomposition temperatures determined by TGA were in the range of 328 to 383 °C depending on the molecular weight, composition, and side chain of the copolymers. It was observed that higher molecular weights led to higher T g values and decomposition temperatures. While copolymers with aliphatic side chains exhibited a single-step decomposition profile, the decomposition of copolymers having aromatic side chains occurred in multiple steps. The variations in the molecular weight, composition, and side chains of the copolymers resulted in a library of tailorable amphiphilic copolymers suitable for multiple applications ranging from biomedical applications to composite manufacturing.

Amphiphilic Polyoxazoline Copolymer–Imidazole Complexes as Tailorable Thermal Latent Curing Agents for One-Component Epoxy Resins

“…This behavior can be related to the glass transition temperature ( T g ) of the copolymers. As the content of the 2-pentyl side group was increased in the copolymer, T g had a decreasing trend with values of 18 °C and −3 °C for PEOZ–PPeOZ 75:25 1K and PEOZ–PPeOZ 25:75 1K, respectively . In other words, the low T g value and the wax form of the PEOZ–PPeOZ 25:75 1K copolymer have led to the dissolution of the copolymer matrix in DGEBA at lower temperatures and subsequent early release of the entrapped Im compared to the PEOZ–PPeOZ 75:25 1K copolymer.…”

“…Furthermore, it should be noted that the effects of polyoxazolines on the thermal, mechanical, and adhesive properties of the manufactured epoxy parts remain to be investigated and are being studied in our group. procedures reported by our group 30 and synthetic procedures are available in SI (1.1.). Copolymers were synthesized through the copolymerization procedure and conditions reported by our group.…”

“…PrOZ and PeOZ monomers were synthesized following the procedures reported by our group and synthetic procedures are available in SI (1.1.). Copolymers were synthesized through the copolymerization procedure and conditions reported by our group .…”

“…PrOZ and PeOZ monomers were synthesized following the procedures reported by our group and synthetic procedures are available in SI (1.1.). Copolymers were synthesized through the copolymerization procedure and conditions reported by our group . Shortly, polymerizations were conducted in round-bottom flasks dried at 120 °C, cooled under vacuum, and treated with vacuum/N 2 cycles.…”

“…Owing to their unique properties such as controlled synthesis, tunability of properties, versatility, and stimuli-responsiveness, POZs have attracted attention for applications in different fields with a major focus on biomedical applications. − 2-oxazoline monomers carrying a variety of functionalities such as aryl or alkyl group can be synthesized through developed methods and later polymerized through cationic ring-opening polymerization (CROP). − The versatility of 2-oxazoline monomers paves the way to obtain polymers with desired chemical, physical, and mechanical properties . Moreover, functionalities of the obtained polymers can be tuned by implementing proper initiating and terminating groups .…”