Owing to their low toxicity, biocompatibility and biodegradability, aliphatic poly(carbonate)s have been widely studied as materials for biomedical application. Furthermore, the synthetic versatility of the six-membered cyclic carbonates for the realization of functional degradable polymers by ring-opening polymerisation has driven wider interest in this area. In this review, the synthesis and ring-opening polymerisation of functional cyclic carbonates that have been reported in the literature in the past decade are discussed. Finally, the post-polymerisation modification methods that have been applied to the resulting homopolymers and copolymers and the application of the materials are also discussed.

No abstract

Sowing the seeds: A simple strategy based on self-seeding allows large single crystals of long regioregular poly(3-hexylthiophene) chains to be grown from solution. When appropriately crystallized, materials differing in their degrees of regioregularity and molecular weights formed monoclinic form II crystals with interdigitated hexyl side groups (see picture).

We describe the organocatalytic depolymerization of poly(ethylene terephthalate) (PET), using a commercially available guanidine catalyst, 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD). Postconsumer PET beverage bottles were used and processed with 1.0 mol % (0.7 wt %) of TBD and excess amount of ethylene glycol (EG) at 190 C for 3.5 hours under atmospheric pressure to give bis(2-hydroxyethyl) terephthalate (BHET) in 78% isolated yield. The catalyst efficiency was comparable to other metal acetate/alkoxide catalysts that are commonly used for depolymerization of PET. The BHET content in the glycolysis product was subject to the reagent loading. This catalyst influenced the rate of the depolymerization as well as the effective process temperature. We also demonstrated the recycling of the catalyst and the excess EG for more than 5 cycles. Computational and experimental studies showed that both TBD and EG activate PET through hydrogen bond formation/activation to facilitate this reaction. V

3D patterning by means of probe‐assisted thermal decomposition has been achieved on phthalaldehyde polymer films with 1 nm vertical resolution and 40 nm lateral resolution. Highly efficient patterning is enabled by a self‐amplified depolymerization mechanism. Pixel writing speeds on the order of microseconds are demonstrated.

No abstract

Alcohol adducts of the N-heterocyclic carbene, 1,3,4-triphenyl-4,5-dihydro-1H-1,2-triazol-5-ylidene (NHC), function as excellent single-component catalyst/initiators for the ring-opening polymerization of lactide and β-butyrolactone. Their reversible dissociation at elevated temperatures generates alcohol and triazolylidene carbene to provide a facile entry to polymerization of cyclic esters on demand. Under optimum conditions, adverse transesterification reactions are minimized, and importantly, upon complete consumption of monomer, a second monomer addition facilitates additional polymer growth, even after precipitation. Block copolymers were prepared by combining disparate polymerization techniques from the use of oligo-adducts and bifunctional initiators. Additionally, more complex polymer architectures were prepared from multifunctional or dendritic initiators, further demonstrating the versatility of the N-heterocyclic carbene platform.

The preparation of cyclic macromolecules has always represented a challenging task for polymer science, mainly because of difficulties in connecting chain extremities together. Initiated by the pioneering studies of Jacobson and Stockmayer, preparative pathways to cyclic polymers have been considerably improved within the last two decades thanks to the advent of both controlled polymerizations and efficient coupling reactions in organic chemistry. This Review aims to provide a critical up-to-date overview and illustrate the considerable efforts that have been made in the past few years to improve the availability of macrocycles for industrial and academic investigations through the use of the ring-closure approach. Particular attention is paid to methods for the preparation of monocycles over more complex architectures, since the latter are usually derived from the former.