Facile one-spot synthesis of highly branched polycaprolactone

Reported is the first solvent-free (bulk) synthesis of degradable/bioresorbable, highly branched polymers via tin octanoate Sn(Oct2) catalysed controlled ring opening co-polymerisation (ROP) of mono and di-functional lactone monomers that proceed to near quantitative conversion. The successful isolation of solvent soluble, highly branched structures was shown to be dependent on both the concentration of the di-functional monomer and the overall reaction time. Comparison with analogous systems utilising controlled radical polymerisation (CRP) to form the highly/hyper branched polymers suggested significant experimental differences between the two chain growth methods. The maximum proportion of di-functional monomer without gelation ensuing was found to be 0.6 equivalents w.r.t. mono-functional monomer (c.f. 1 with CRP) and the onset of significant levels of branching occurred at approximately 90% conversion (c.f. ~70% with CRP). These differences and significant disparity in reaction times were attributed to (a) the coordination and insertion (C+I) propagation mechanism adopted by the Sn catalyst and (b) the presence of additional trans-esterification reactions at high conversion. Evidence is presented to support the conclusion that there are two mechanisms contributing to the overall branching process in the ROP system at high conversion. First, the C+I mechanism promotes growth of linear polymer until approximately 90% conversion, after which both the C+I and trans-esterification processes contribute to the interchain branching process. The branched nature of the molecular structures was supported by confirmation plots generated from static light scattering. This data demonstrated that the polymers synthesised exhibit varying degrees of branching, consistent with the di-functional monomer (4,4’-bioxepanyl-7,7’-dione - BOD) concentration in the feed. The degree of branching was calculated using 3 different methods and the results were shown to be independent of method. Finally, DSC analysis of the polymers demonstrated correlation between the degree of branching achieved and the observed Tm for the material where increased branching leads to a drop in the recorded Tm

Development Of Smart Polydiacetylene Micelles For In Vitro And In Vivo Tracking

Polydiacetylenes (PDAs) are conjugated polymers that can form highly ordered structures with unique chromatic features. PDAs are typically obtained by polymerisation of diacetylene (DA) monomers using ultraviolet (UV) light irradiation without the need of any initiators, which generates a polymeric backbone with alternating C=C and C≡C bonds (one-yne), giving a blue non-fluorescent PDAs. Several stimuli, such as pH, temperature and ligand-receptor interaction, can induce a red-shift and weakly fluorescent colorimetric transition that makes PDAs a very interesting system in the field of sensors and drug delivery systems [1,2]. PDAs systems are usually prepared using amphiphilic commercial monomers like 10,12 - pentacosadyinoic acid (PCDA) and 10,12 - tricosadyinoic acid (TCDA), with the addition in the final formulation of  phospholipids [3] and/or water-soluble polymers [4], that can influence PDAs system sensitivity, stability and drug-released properties. In the present project, we selected poly(glycerol adipate) (PGA) as a novel  greener polymeric alternative to develop PDAs mixed-micelles. The addition of PGA will confer to the final formulations biodegradability and biocompatibility [5]. Furthermore, PGA can self-assembly into nanoparticles (NPs) in aqueous media using nanoprecipitation method, which is highly compatible with traditional process for the formation of PDAs [6]. Due to PGA low toxicity and possibility to produce active polymeric prodrugs by drug coupling to the PGA backbone, PDA/PGA mixed-micelles can be considered a potential platform intrinsically biodegradable which may facilitate in vivo and in vitro tracking of delivery systems [7]. [1] X. Qian and B. Stadler, Chem. Mater. 2019, 31(4), 1196-1222. [2] F. Fang, F. Meng, L. Luo, Mater. Chem. Front. 2020, 4(4), 1089,1104 [3] G.P. Camilloto, C.G. Otoni, G.W.R. de Almeida, I.R.N de Oliveira, L.H.M. da Silva, A.C. dos Santos Pires, N. De F.F. Soares. ACS Food Sci. Technol. 2021, 1(5), 745-753. [4] A. Pankaew, N. Traiphol, R. Traiphol, Colloids Surf. Physicochem. Eng. Asp. 2021, 608, 125626. [5] P.L. JacobsL.A. Ruiz Cantu, A.K. Pearce, Y. He, J.C. Lentz, J.C. Moore, F.Machado, G.Rivers, E. Apebende, M.R. Fernandenz, I. Francolini, R. Wildman, S.M. Howdle, V. Taresco, Poly (Glycerol Adipate) (PGA) Backbone Modifications with a Library of Functional Diols: Chemical and Physical Effects. Polymer, 228, 123912 [6] P. Kallinteri, S. Higgins, G.A. Hutcheon, C.B. St Pourcain, M.C. Garnett. Biomacromolecules

Starch/Poly (Glycerol-Adipate) Nanocomposite Film as Novel Biocompatible Materials

Starch is one of the most abundant polysaccharides on the earth and it is the most important source of energy intake for humans. Thermoplastic starch (TPS) is also widely used for new bio-based materials. The blending of starch with other molecules may lead to new interesting biodegradable scaffolds to be exploited in food, medical, and pharmaceutical fields. In this work, we used native starch films as biopolymeric matrix carriers of chemo enzymatically-synthesized poly (glycerol-adipate) (PGA) nanoparticles (NPs) to produce a novel and biocompatible material. The prototype films had a crystallinity ranging from 4% to 7%. The intrinsic and thermo-mechanical properties of the composite showed that the incorporation of NPs in the starch films decreases the glass transition temperature. The utilization of these film prototypes as the basis for new biocompatible material showed promise, particularly because they have a very low or even zero cytotoxicity. Coumarin was used to monitor the distribution of the PGA NPs in the films and demonstrated a possible interaction between the two polymers. These novel hybrid nanocomposite films show great promise and could be used in the future as biodegradable and biocompatible platforms for the controlled release of amphiphilic and hydrophobic active ingredients

Versatile, Highly Controlled Synthesis of Hybrid (Meth)acrylate–Polyester–Carbonates and their Exploitation in Tandem Post-Polymerization–Functionalization

The use of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) as a mild catalyst for the ring-opening polymerization (ROP) of the pharma-friendly and biodegradable monomer lactide and a functionalizable tert-butyloxycarbonyl (BOC)-protected cyclic carbonate is explored. Successful and controlled ROP is demonstrated when employing a series of labile-ester (bis)(meth)acrylate initiators to produce macromonomers suitable for a range of post-polymerization modifications. Importantly, the use of DBU ensured retention of the BOC group of the carbonate monomer during the polymerization, thus facilitating the production of highly functionalizable hybrid materials unobtainable using the more reactive triazabicyclodecene (TBD). Subsequently, a variety of short homo- and copolymers are synthesized with good control over material properties and final polymer composition. Successful attainment of these short copolymers confirm that DBU can overcome the previously observed limitations of TBD related to its kinetic competition between ROP and transesterification side-reactions under these reaction conditions. Furthermore, the fidelity of the hydroxyl and (meth)acrylic end groups are maintained as confirmed by a series of secondary tandem reactions. The macromonomers are also utilized in reversible addition−fragmentation chain-transfer polymerization (RAFT) polymerization for the production of amphiphilic block or random copolymers with a hydrophilic comonomer, poly(ethyleneglycol)methacrylate. The amphiphilic copolymers produced via the tandem RAFT reaction demonstrate the ability to self-assemble into monodisperse nanoparticles in aqueous environments.</p