Juan C. Ronda

Plant Oils as Platform Chemicals for Polyurethane Synthesis: Current State-of-the-Art

Plant oils are already one of the most important platform chemicals for the chemical industry due to its universal availability, inherent biodegradability, and low price. Nowadays, plant oils are already a commercial source of multifunctional monomers and oligomers for polyurethane synthesis, and the design of novel biobased polyols derived from them is an active area of research. By taking advantage of the wide variety of possibilities for chemical modification of plant oils, there is a broad palette of strategies to functionalize its structure with hydroxyl groups. The purpose of this review is to comprehensively overview recent developments on the preparation of biobased polyols from plant oils, covering from the general epoxidation and ring-opening approach to novel routes based on thiol-ene click chemistry as well as to highlight the properties of polyurethanes obtained from them.

Polybenzoxazines: new players in the bio-based polymer arena

Polybenzoxazines are phenol-like materials that have attracted significant attention from both academia and industry because of their unique advantages. The growth of this technology has always been linked to petro-based feedstocks. However, due to the incessant global energy crisis it is now finding a breakthrough through the preparation of their monomers from renewable resources. This mini-review focuses on the recent efforts to replace petro-based feedstocks with polybenzoxazine precursors.

Thiol–yne reaction of alkyne-derivatized fatty acids: biobased polyols and cytocompatibility of derived polyurethanes

With the goal of obtaining renewable diols and polyols for polyurethane (PU) technology, the thiol–yne coupling reaction was applied to alkyne-derivatized fatty acids derived from naturally occurring oleic and 10-undecenoic acids. The resulting monomers were then polymerized with 4,4′-methylenebis(phenylisocyanate) to produce the corresponding PUs. The chemical structures and thermal and mechanical properties of the synthesized PUs have been evaluated by FTIR and NMR spectroscopy, DSC, TGA and tensile tests respectively. Moreover, the biocompatibilities of the synthesized PUs with human osteoblast-like cell line (MG63) have also been evaluated for tissue engineering purposes.

Convenient and solventless preparation of pure carbon nanotube/polybenzoxazine nanocomposites with low percolation threshold and improved thermal and fire properties

This work contemplates the use of pristine multiwalled carbon nanotubes (MWNTs) as nanofillers in the preparation of bisphenol A-based polybenzoxazine and diphenolic acid derived polybenzoxazine. These materials were prepared by using a solventless method varying the MWNT amount from 0.1 to 1.0 wt%. MWNTs were found to disperse well within both benzoxazine monomers and the dispersion also appears to be good in the cured system. Rheological and electrical percolation thresholds were obtained for MWNT concentrations lower than 0.1 wt% indicating the existence of good affinity between MWNTs and polybenzoxazine matrices. The characterization of the resulting nanocomposites revealed that MWNTs affected polybenzoxazines differently. The limiting oxygen index of the nanocomposites increased as a function of the nanotube content, from 35.2 to 38.7 for a bisphenol A-benzoxazine based system (BPA-PBz) and from 31.2 to 37.4 for a methyl-4,4′-bis-[6-(3-phenyl-3,4-dihydro-2H-1,3-benzoxazine)]pentanoate based system (MDP-PBz), respectively. Moreover, MWNTs positively influenced the thermo-mechanical, thermal and mechanical properties of the nanocomposites. The resulting attractive properties have been attributed to good interaction between the polybenzoxazines and the finely dispersed nanofillers.

Enhancement of Fatty Acid-based Polyurethanes Cytocompatibility by Non-covalent Anchoring of Chondroitin Sulfate

For tissue engineering purpose biopolymer chondroitin sulfate (CS), one of the major components of cartilage and bone extracellular matrix, was immobilized onto the surface of amino-functionalized polyurethane (PU) films derived from naturally occurring oleic and 10-undecenoic acids. The amino-functionalized PUs were prepared by aminolysis with 1,6-hexamethylenediamine of synthesized PUs containing methyl ester groups. FTIR-ATR, XPS, SEM, and water contact angle measurements were used to confirm the surface changes at each step of treatment, both in morphologies and chemical composition. Cytotoxicity and cell morphology analysis using osteoblast cell line MG63 showed that PU-CS films are suitable materials for cell growth, spreading, and differentiation.

Polyketoesters from oleic acid. Synthesis and functionalization

In this study, we exploited the reactivity of the methyl oleate enone derivative for the conversion of this renewable raw material to ketone-containing hydroxyesters. The radical-mediated thiol–ene addition to the conjugated double bonds has been investigated and low yields were obtained due to secondary reactions. The thiol-Michael addition under acidic and basic/nucleophilic conditions was also examined. While using vanadyl triflate (VO(OTf)2), a slight excess of thiol was necessary to complete the reaction, by using both basic/nucleophilic catalysts 1,5-diazabicyclo[4.3.0]non-5-ene (DBN) and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), quantitative conversion was achieved under stoichiometric conditions in shorter reaction times. The obtained hydroxyester, carrying sulphide and ketone functional groups, was used to obtain polyesters by Novozyme-435 enzymatic polymerization. The coupling between the ketone group of the repeating unit and a model oxyamine has been used to demonstrate the polyketoester functionalization via oxime formation.

Study on the interaction between gelatin and polyurethanes derived from fatty acids

In this study, gelatin was blended to proprietary noncytotoxic polyurethanes (PU) derived from vegetable oils with different weight ratios, as material for the preparation of novel biomedical products. The PU/gelatin blends were characterized for their morphology through scanning electron microscopy. Mechanical and thermal properties, chemical interactions between components, degradation behavior, surface properties, cell adhesion, and bioactivity were investigated as a function of the protein content. Higher blend miscibility was observed for the amorphous PUs, derived from oleic acid. Properties of PU/gelatin films were strongly influenced by the concentration of gelatin in the films. Gelatin enhanced the hydrophilicity, bioactivity, and cell adhesion of PUs.

Antimicrobial polyurethane thermosets based on undecylenic acid: synthesis and evaluation.

In the present study, plant oil-derived surface-modifiable polyurethane thermosets are presented. Polyol synthesis is carried out taking advantage of thiol-yne photopolymerization of undecylenic acid derivatives containing methyl ester or hydroxyl moieties. The prepared methyl ester-containing polyurethanes allow surface modification treatment to enhance their hydrophilicity and impart antimicrobial activity through the following two steps: i) grafting poly(propylene glycol) monoamine (Jeffamine M-600) via aminolysis and ii) Jeffamine M-600 layer complexation with iodine. The antimicrobial activity of the iodine-containing polyurethanes is demonstrated by its capacity to inhibit the growth of Staphylococcus aureus, and Candida albicans in agar media.

Chapter 5 – Tailoring Polybenzoxazine Chemical Structure: Synthetic Approaches to Flexible Systems

In this chapter we present synthetic strategies to incorporate flexible segments into polybenzoxazine precursors such as monomers, oligomers, and polymers. In this way, a new class of flexible thermoset polybenzoxazines, with thermal and mechanical properties and enhanced processability, has been developed, allowing for potential new applications for these polymers. Strategies successfully employed include monomer and polymer synthesis based on Mannich, hydrosilylation, metathesis, classical polycondensations, and Huisgen type click reactions.

Polybenzoxazine foams: Modeling mechanical properties

Flame-retardant polybenzoxazine foams containing 1% phosphorus were prepared from diphenolic acid-based benzoxazine and 9,10-dihydro-9-oxa-10-(1-hydroxy-1-methylethyl)phosphaphenanthrene-10-oxide. Statistical predictive models were developed to determine the influence of the foaming time (tf) and foaming temperature (Tf) on the density, compressive modulus, and compressive strength of the foams. Results showed that the density of the foams exhibited great dependence on tf, whereas both compressive properties were more dependent on Tf and tf. Additionally, the flammability of the foams was also characterized by the limiting oxygen index. The presence of 9,10-dihydro-9-oxa-10-(1-hydroxy-1-methylethyl)phosphaphenanthrene-10-oxide greatly improved the flame retardancy of the resulting foams.