Synthesis of hydrocarbon polymers by cationic polymerization and their thermal properties

Abstract

Cationic homo-and co-polymerization of indene (Ind), styrene (St), limonene (Lim), and 5-ethylidene-2-norbornene (ENB) was performed with AlCl 3 in dichloroethane at À20°C under inert N 2 . The aim of this work is to investigate the effect of the reaction conditions on the molecular weight of polyindene (PInd) obtained by cationic polymerization with AlCl 3 without an electron donor, and also to determine the effect of the use of cyclic diolefin comonomers on the polymer properties. The polymers were synthesized at a monomer/catalyst molar ratio (MR) of 100; St and Lim showed the highest and lowest reactivity, respectively. The polymers were characterized by 13 C and 1 H NMR spectroscopy, Fourier transform infrared spectroscopy, ultraviolet-visible spectroscopy, size exclusion chromatography, differential scanning calorimetry, and thermogravimetric analysis. PInd with a number average molecular weight (M n ) of 45 Â 10 3 g/mol and a glass transition temperature (T g ) of 207°C was obtained, whereas only oligomeric polylimonenes were obtained. Cyclic diolefins depressed both the M n and T g values of the Ind-copolymers. There was a dramatic decrease in the M n of the polymers: those obtained at a MR of 1:1 in the feed presented M n values lower than 10 4 g/mol, with the exception of poly(Ind-co-ENB), which is cross-linked. Poly(Ind-co-Lim) with lateral double bonds, a comonomer content of 1 to 20 mol%, and T g values in the range of 140-200°C were obtained.

Copolymerization of Limonene with n‐Butyl Acrylate

“…The peaks of the –OCH 2 group for BA are located at ∼4.0 ppm; the peaks for the limonene endocyclic and exocyclic double bonds are located at 5.4 and 4.7 ppm, respectively. As the endocyclic double bond of limonene is very stable, it is a reasonable assumption that only the exocyclic double bonds participated in the polymerization, whereas the endocyclic double bonds remained in the polymer chain. Thus, the following equation was used to calculate copolymer composition: where A 4.0 refers to the peak area at δ = 3.8–4.2 which corresponds to the –OCH 2 –protons of BA (“D” in Figure ), and A 5.4 refers to the endocyclic double bond of limonene (“a” in Figure ).…”

“…Limonene (C 10 H 16 ) is an unsaturated cyclic hydrocarbon which possesses two non‐conjugated double bonds: an endocyclic double bond and an exocyclic double bond, both of which provide potential for polymerization (see Figure (a)). However, because of the ring strain energy and steric impediments, the endocyclic double bond of limonene shows a much lower reactivity than the exocyclic vinyl group during polymerization . The polymerization of limonene has been studied since the 1950 s .…”

“…Early attempts at d‐limonene solution polymerization using Lewis acids and Ziegler–Natta catalysts yielded low molecular weight products ( M w = ∼1 000, less than 10 repeat units) . Cationic polymerization efforts yielded a much lower limonene conversion (7%) than styrene (92%) under the same conditions . In the cationic copolymerization of limonene with indene, a non‐polar olefin, limonene exhibited low reactivity and acted as a chain‐transfer agent by presenting low co‐monomer incorporation and decreased molecular weights.…”

Free‐radical terpolymerization of n‐butyl acrylate/butyl methacrylate/d‐limonene

“…Many studies have shown that limonene has a high propensity toward chain‐transfer reactions, as the allylic hydrogens next to the double bonds are very reactive and tend to be easily captured by living radicals . During polymerization, molecular weight development is greatly influenced by this chain‐transfer reaction mechanism.…”

Progress in the synthesis of sustainable polymers from terpenes and terpenoids

“…62 The polymerisation of 6 was first carried out by Roberts and Day 37 by using Friedel-Crafts conditions; early attempts were capable of producing only lowmolecular weight polymers. The cationic polymerisation of limonene (6) using AlCl 3 as a catalyst was studied by Brum et al 63 The poly(limonene) (32) (Scheme 5) produced had a very low molecular weight (c. 0·5 kDa), and low conversions of only 7% were achieved; this is likely attributed to chain termination by way of b-elimination. Satoh et al 64 were able to synthesise a …”