Isocyanate-Free Approach to Water-Borne Polyurea Dispersions and Coatings

Synthesis, Structure and Properties of Polyester Polyureas via a Non-Isocyanate Route with Good Combined Properties

Polyureas have been widely applied in many fields, such as coatings, fibers, foams and dielectric materials. Traditionally, polyureas are prepared from isocyanates, which are highly toxic and harmful to humans and the environment. Synthesis of polyureas via non-isocyanate routes is green, environmentally friendly and sustainable. However, the application of non-isocyanate polyureas is quite restrained due to their brittleness as the result of the lack of a soft segment in their molecular blocks. To address this issue, we have prepared polyester polyureas via an isocyanate-free route and introduced polyester-based soft segments to improve their toughness and endow high impact resistance to the polyureas. In this paper, the soft segments of polyureas were synthesized by the esterification and polycondensation of dodecanedioic acid and 1,4-butanediol. Hard segments of polyureas were synthesized by melt polycondensation of urea and 1,10-diaminodecane without a catalyst or high pressure. A series of polyester polyureas were synthesized by the polycondensation of the soft and hard segments. These synthesized polyester-type polyureas exhibit excellent mechanical and thermal properties. Therefore, they have high potential to substitute traditional polyureas.

Polymers without Petrochemicals: Sustainable Routes to Conventional Monomers

Access to a wide range of plastic materials has been rationalized by the increased demand from growing populations and the development of high-throughput production systems. Plastic materials at low costs with reliable properties have been utilized in many everyday products. Multibillion-dollar companies are established around these plastic materials, and each polymer takes years to optimize, secure intellectual property, comply with the regulatory bodies such as the Registration, Evaluation, Authorisation and Restriction of Chemicals and the Environmental Protection Agency and develop consumer confidence. Therefore, developing a fully sustainable new plastic material with even a slightly different chemical structure is a costly and long process. Hence, the production of the common plastic materials with exactly the same chemical structures that does not require any new registration processes better reflects the reality of how to address the critical future of sustainable plastics. In this review, we have highlighted the very recent examples on the synthesis of common monomers using chemicals from sustainable feedstocks that can be used as a like-for-like substitute to prepare conventional petrochemical-free thermoplastics.

Synthetic Sugar-Only Polymers with Double-Shoulder Task: Bioactivity and Imaging

The search for novel fluorescent materials has attracted the attention of many researchers. Numerous bioimaging materials based on the aggregation-induced emission (AIE) units have been surging and could be employed in wide areas during the past two decades. In recent few years, the appearance of nonconventional fluorescence emitters without aromatic conjugated structures provides another bioimaging candidate which has the advantage of enhanced biodegradability and relatively low cost, and their luminescent mechanism can be explained by clustering-triggered emission (CTE) like AIE. In our contribution, we utilize nonaromatic sugar as a monomer to prepare a series of glycopolymers with designed components through sunlight-induced reversible addition fragmentation chain transfer polymerization; these glycopolymers can be employed in bioimaging fields due to the bioactivity coming from sugar and CTE capacity.

Direct synthesis of polyureas from the dehydrogenative coupling of diamines and methanol

We report here the first example of the direct synthesis of polyureas from the dehydrogenative coupling of diamines and methanol using a ruthenium pincer catalyst. The present methodology replaces the use of toxic diisocyanates, conventionally used for the production of polyureas, with methanol, which is renewable, less toxic, and cheaper, making the overall process safer and more sustainable. Further advantages of the current method have been demonstrated by the synthesis of a renewable, a chiral, and the first 13C-labelled polyurea.

Chemical recycling of poly-(bisphenol A carbonate) by diaminolysis: A new carbon-saving synthetic entry into non-isocyanate polyureas (NIPUreas)

The present study describes an unprecedented approach to valorize potentially hazardous poly-(bisphenol A carbonate) (PC) wastes. In THF, under non-severe conditions (120 °C), the reaction of PC with long-chain diamines H₂NRNH₂ (2 equivalents) provided a tool to regenerate the monomer bisphenol A (BPA; 83-95%, isolated) and repurpose waste PC into [-NHRNHCO-]_n polyureas (PUs; 78-99%, isolated) through a non-isocyanate route. Basic diamines (1,6-diaminohexane, 4,7,10-trioxa-1,13-tridecanediamine, meta-xylylenediamine, para-xylylenediamine) reacted with PC without any auxiliary catalyst; less reactive aromatic diamines (4,4'-diaminodiphenylmethane, 2,4-diaminotoluene) required the assistance of a base catalyst (1,8-diazabicyclo[5.4.0]undec-7-ene, NaOH). The formation of [-NHRNHCO-]_n goes through a carbamation step affording BPA and carbamate intermediates H[-OArOC(O)NHRNHC(O)-]_nOArOH (Ar=4,4'-C₆H₄C(Me)₂C₆H₄-) that, in a subsequent step, convert into [-NHRNHCO-]_n and more BPA. All the PUs were characterized in the solid state by CP/MAS ¹³C NMR (δ(CO) = 152-161 ppm) and IR spectroscopy. The positions of ν(N-H) and ν(CO) absorptions are typical of "hydrogen-bonded ordered" bands suggesting the presence of H-bonded groups in network structures characterized by some degree of order or regularity. DSC and TGA analyses showed that the PUs are thermally stable (T_d,5%: 212-270 °C) and suitable for being processed since their degradation begins at temperatures about 100 °C higher than their T_g or T_m.

Water-based non-isocyanate polyurethane-ureas (NIPUUs)

This review aims at discussing the achievements and the remaining challenges in the development of water-soluble NIPUUs, NIPUUs-based hydrogels and water-borne NIPUU dispersions.

Direct Synthesis of Polyurea Thermoplastics from CO2 and Diamines

The transformation of CO₂ into polymeric materials is an important and hot research topic from the viewpoint of renewable resources and environmental effects. Herein, a series of polyureas have been synthesized by polycondensation from CO₂ with diamines of 1,12-diaminododecane (DAD) and/or 4,7,10-trioxa-1,13-tridecanediamine (TTD). The properties of polyureas synthesized were characterized by FTIR, ¹H NMR, ¹³C NMR, XRD, DSC, TGA, and DMA. The polyureas synthesized from CO₂ with a mixture of diamines presented high performances compared to those of polyureas synthesized from CO₂ with a single diamine. The thermal and mechanical properties were improved largely by the variation in the crystallization and the chain flexibility depending on the changes in the density and/or intensity of hydrogen bonds. With increasing amounts of TTD from 0 to 100% in weight, the melting (T_m), crystallization (T_c), and glass transition (T_g) temperatures decreased from 207 to 116 °C, from 181 to 54 °C, and from 66 to -34 °C, respectively. When the TTD content was increased from 0 to 50 wt %, the Young's modulus decreased from 1170 to 406 MPa, and the tensile strength decreased from 53.3 to 42.9 MPa. However, the elongation at break increased from 13 to 330%. Furthermore, the chain length of aliphatic diamines and polyetheramines had a significant effect on the mechanical properties. The initial decomposition temperature (T_d,5%) is >295 °C, about 110 °C higher than the T_m (116-207 °C), which is advantageous for the postprocessing. The mechanical properties of the polyureas synthesized herein are superior to those of polycarbonate and polyamide 6. Thus, polyureas synthesized from the renewable and cheap resources, CO₂ and diamines, will find wide potential applications in the field of polymeric materials.

Investigations on Aging Behavior and Mechanism of Polyurea Coating in Marine Atmosphere

In this investigation, the aging behaviors of polyurea coating exposed to marine atmosphere for 150 days were studied and the mechanism was analyzed. The influences on surface and mechanical properties, surface morphology, thermal stability behavior, as well as chemical changes evolution of the coating were investigated. By attenuated total reflectance fourier transform infrared spectroscopy (ATR–FTIR) and X-ray photoelectron spectroscopy (XPS), changes in the chemical properties of polyurea coatings before (PCB) and after 150 d (PCA) of aging were analyzed, and emphasis was given to the effect of aging on functional group change, the hydrogen bonding behavior, and phase separated morphology. The results displayed prominent chain scission during aging, such as N–H, C=O, and C–O–C and the hydrogen bonded urea carbonyl content showed a decrease trend. The relative content of soft and hard segments showed a significant change, which increased the degree of phase separation.

t-Butyl-Oxycarbonylated Diamines as Building Blocks for Isocyanate-Free Polyurethane/Urea Dispersions and Coatings

t-Butyl-oxycarbonylated diamines ("di-Boc-carbamates") are investigated as dicarbamate monomers for diamine/dicarbamate polymerizations. Polyureas (PUs) and polyurethanes (PURs) with high molecular weights are prepared from stoichiometric polymerizations of diamines or diols with N-N'-di-t-butyl-oxycarbonyl isophorone diamine (DiBoc-IPDC) using KOt-Bu as a catalyst, while gelation is observed when an excess of DiBoc-IPDC is used with respect to the diamines or diols. Stable dispersions are obtained from PUs and PURs with 3,3'-diamino-N-methyldipropylamine (DMDPA) as internal dispersing agent. The corresponding PU-based coatings exhibit superior mechanical properties and solvent resistances compared to the polyurethane urea coatings synthesized from diols, DiBoc-IPDC, and DMDPA.