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Polymers based on renewable monomers are projected to have a significant role in the sustainable economy, even in the near future. Undoubtedly, the cationically polymerizable β-pinene, available in considerable quantities, is one of the most promising bio-based monomers for such purposes. In the course of our systematic investigations related to the catalytic activity of TiCl4 on the cationic polymerization of this natural olefin, it was found that the 2-chloro-2,4,4-trimethylpentane (TMPCl)/TiCl4/N,N,N′,N′-tetramethylethylenediamine (TMEDA) initiating system induced efficient polymerization in dichloromethane (DCM)/hexane (Hx) mixture at both −78 °C and room temperature. At −78 °C, 100% monomer conversion was observed within 40 min, resulting in poly(β-pinene) with relatively high Mn (5500 g/mol). The molecular weight distributions (MWD) were uniformly shifted towards higher molecular weights (MW) in these polymerizations as long as monomer was present in the reaction mixture. However, chain–chain coupling took place after reaching 100% conversion, i.e., under monomer-starved conditions, resulting in considerable molecular weight increase and MWD broadening at −78 °C. At room temperature, the polymerization rate was lower, but chain coupling did not occur. The addition of a second feed of monomer in the polymerization system led to increasing conversion and polymers with higher MWs at both temperatures. 1H NMR spectra of the formed polymers indicated high in-chain double-bond contents. To overcome the polarity decrease by raising the temperature, polymerizations were also carried out in pure DCM at room temperature and at −20 °C. In both cases, rapid polymerization occurred with nearly quantitative yields, leading to poly(β-pinene)s with Mns in the range of 2000 g/mol. Strikingly, polymerization by TiCl4 alone, i.e., without any additive, also occurred with near complete conversion at room temperature within a few minutes, attributed to initiation by adventitious protic impurities. These results convincingly prove that highly efficient carbocationic polymerization of the renewable β-pinene can be accomplished with TiCl4 as catalyst under both cryogenic conditions, applied widely for carbocationic polymerizations, and the environmentally benign, energy-saving room temperature, i.e., without any additive and cooling or heating. These findings enable TiCl4-catalyzed eco-friendly manufacturing of poly(β-pinene)s, which can be utilized in various applications, and in addition, subsequent derivatizations could result in a range of high-added-value products.

Quasiliving atom transfer radical polymerization (ATRP) of non-fluorous monomers, styrene and n-butyl acrylate, was attempted in benzotrifluoride (BTF; α,α,α-trifluorotoluene, TFT), the simplest trifluoromethylated aromatic compound, as an alternative solvent to widely used polymerization media in ATRP and other radical polymerizations, such as benzene, toluene, xylene, diphenylether etc., with toxic, carcinogenic or corrosive labels. In the absence of any other fluorinated additive, BTF was found to be a suitable reaction medium for ATRP of these monomers with the CuBr/N,N,N′,N″,N″-penta-methyldiethylenetetramine (PMDETA) non-fluorous catalyst system at 90 °C. The higher number average molecular weights than that of the theoretical ones at relatively low conversions in styrene polymerization with the 1-phenylethyl bromide (PhEtBr) initiator indicates quasiliving polymerization of styrene in BTF with slow initiation. This is confirmed by the linear correlation of the obtained data in the slow initiation plot, i.e. ln(1− f ) + f versus ln(1− C ), where f and C stand for the initiating efficiency and conversion, respectively. Quasiliving ATRP of n-butyl acrylate with rapid quantitative initiation was found by the ethyl-2-bromoisobutyrate (Et-2Br i Bu)/CuBr/PMDETA initiating system in BTF. In both cases, the absence of any kind of significant side reactions, i.e. chain transfer to solvent or irreversible termination, was observed. Thus, in contrast to the general perception of the immiscibility between fluorous and non-fluorous solvent/polymer systems, our findings indicate that BTF, as a fluorinated solvent, due to its unique properties, including its moderately high polarity, low vapor pressure and low toxicity etc., can be considered as an outstanding solvent with broad application possibilities for a large array of polymerization reactions and other chemical processes of non-fluorous monomers, polymers and many other compounds as well.