100th Anniversary of Macromolecular Science Viewpoint: Polymerization of Cumulated Bonds: Isocyanates, Allenes, and Ketenes as Monomers

Abstract

Polymer chemistry offers exciting opportunities to tailor the properties of soft materials through control of the composition of the polymers and their interaction with each other, additives, and surfaces. Ongoing advances in the synthesis of polymeric materials demonstrate the drive for materials with tailored properties for enhanced performance in the next generation of materials and devices. One class of small molecules that can serve as monomers in chain growth polymerization are cumulated double bonds of the general form XYZ. The three most common classes of these molecules are isocyanates (NCO), allenes (CCC), and ketenes (CCO), each of which has been explored as monomers under a variety of conditions. The orthogonality of the two pi bonds of the cumulated double bonds (i.e., lack of conjugation) enables the formation of different polymer backbones from a single monomer, provided the regioreactivity is controlled. This Viewpoint outlines the use of these three cumulated double bonds as monomers, illustrating success and current limitations to established polymerization methods. We then provide an outlook to the future of cumulated double bonds as monomers for the generation of tailored polymer compositions.

Mechanical Properties and Bioactivity of Poly(Lactic Acid) Composites Containing Poly(Glycolic Acid) Fiber and Hydroxyapatite Particles

“…The same bands were observed for the expanded graphite reacted with the isocyanate groups [ 29 ]. The atomic ratio of the urethane groups to the isocyanate groups was almost 1:1, indicating that side reactions including dimerization of HMDI and reaction between HA-HMDI and the impurity such as H 2 O were avoided [ 30 , 31 ]. In N1s spectra of HA-HMDI-EG, the peak of the isocyanate groups at 400.5 eV disappeared after additional urethane bonds were formed between the isocyanate groups of HA-HMDI and hydroxyl groups of EG.…”

Zinc Hydride Catalyzed Chemoselective Hydroboration of Isocyanates: Amide Bond Formation and C=O Bond Cleavage

“…[a] [a] Reaction conditions:i socyanates (0.3 mmol, 1.0 equiv), pinacolborane (0.3 mmol, 1.0 equiv), catalyst I (2 mol %), 2hat rt under N 2 for all the isocyanates but in case of 2g stirred for 4h;2d, 2f,a nd 2u stirred for 15 min;a nd 2i-2o stirred for 10 min. The yield was calculated by 1 HNMR spectroscopy based on isocyanate consumption and identified the NCHOsignal confirmed the product. Formamide (2ee, 2ff, 2mm, 2yy)was isolated as amixture of s-cis and s-trans isomers after hydrolysis in methanol.…”

“…Isocyanates are cheaper and commercially available feedstocks that are very useful in numerous organic transformations. [1] These are essential precursors for the synthesis of extremely important amides. [2] In particular,f ormamides are necessary starting materials to produce useful heterocycles, bioactive compounds,a nd drugs.…”

When Hydrazonoyl Chlorides Meet Allenes: a Site- and Regio-Selective Copper(I)-Catalysed Approach to 5-Substituted Pyrazoles

“…Small quantitites of the target pyrazole (3aa) were obtained in the presence of stoichiometric amounts of silver(I) salts (Table 1, entries 2-5), this finding is consistent to the prolonged reaction times usually required for this kind of reaction. 4 This discouraging picture changed by using a catalytic amount of copper(I) salt (Table 1, entries [6][7][8][9][10][11][12][13][14]. As it can be seen from Table 1, entry 10, the best result was obtained with CuCl in dichloromethane at 20 °C.…”

“…In the case of the two allenes 2d,e bearing electro-neutral or electro-donating groups, respectively, it was not possible to isolate the correponding pyrazole adduct since their extensive decomposition took place ( The latter behaviour is consistent to the well-known polymerisation of allenes in the presence of metal cations, as early reports clearly indicate that cationic techniques gave uncontrolled allene oligomerization and polymerization. 7 Anyway, the 5-substituted pyrazoles (3ad) and (3ae) were obtained by reacting hydrazonoyl chloride (1a) with 3-cyclohexyl-1-propyne (4a) and methoxypropargyl ether (4b), respectively, in the presence of catalytic amounts of CuCl following a recent protocol elaborated by one of us. 8 This pair of reactions is particularly relevant because it provides evidence that allene → acetylene isomerisation is suppressed under the conditions depicted in Scheme 2.…”