Lucas Polo Fonseca

Step‐growth polymerization (SGP) typically produces polymers with exceptional versatility in terms of applications, but its inherently uncontrolled nature leads to broad molecular weight distributions ( Đ ) and consequently polymers with poor nanostructure control in comparison to chain growth polymers. In this study, we provide a solution to this long‐lasting problem by introducing a new concept, asymmetric dynamic bond mediated polymerization (ADBP). In this case, the polymerization between asymmetric and reversibly deactivated AA’‐type dielectrophiles and B ₂ ‐type dinucleophiles has a preferential reaction pathway between the functionality A’ of the asymmetric AA’ monomer with B ₂ . We observe that this polymerization allows us to achieve better control of the step‐growth process where in the first stage only well‐defined trimers and dimers are primarily formed up to conversion ( p ) ≤ 0.6, followed by their polymerization stage ( p ≥ 0.6). This leads to polymers with reduced Đ (Đ = 1.2, which exhibit the ability to form microphase‐separated domains with higher ordering, giving rise to polyurethane thermosets with superior mechanical properties compared to a traditional SGP analog.

Step‐growth polymerization (SGP) typically produces polymers with exceptional versatility in terms of applications, but its inherently uncontrolled nature leads to broad molecular weight distributions ( Đ ) and consequently polymers with poor nanostructure control in comparison to chain growth polymers. In this study, we provide a solution to this long‐lasting problem by introducing a new concept, asymmetric dynamic bond mediated polymerization (ADBP). In this case, the polymerization between asymmetric and reversibly deactivated AA’‐type dielectrophiles and B ₂ ‐type dinucleophiles has a preferential reaction pathway between the functionality A’ of the asymmetric AA’ monomer with B ₂ . We observe that this polymerization allows us to achieve better control of the step‐growth process where in the first stage only well‐defined trimers and dimers are primarily formed up to conversion ( p ) ≤ 0.6, followed by their polymerization stage ( p ≥ 0.6). This leads to polymers with reduced Đ (Đ = 1.2, which exhibit the ability to form microphase‐separated domains with higher ordering, giving rise to polyurethane thermosets with superior mechanical properties compared to a traditional SGP analog.

A real-world laboratory accident highlights underestimated dermal risks posed by reactive isocyanates. First-aid actions and essential safety insights are shared to reinforce best laboratory safety practices.

Switchable adhesives are materials of utmost importance due to their capability of having their adhesion/cohesion properties reversibly triggered upon stimuli, allowing on‐demand surface attaching/detaching. Still, several challenges mainly associated with complex uncontrolled chemical processes hinders their production. In this study, it is found that unexpectedly vinyl ethers are able to react with thiols in the presence of a catalytic concentration of base, which allows the preparation of well‐defined phase‐separated switchable adhesives. Indeed, these findings show that base‐catalyzed thiol‐acrylate and thiol‐vinyl ether are highly orthogonal, making the acrylate reaction faster. This is explored to react in the first stage thiols with acrylates in the presence of vinyl ethers to end‐cap all the oligomers with stable vinyl ethers and suppress undesirable disulfide formation. In a second stage the UV‐triggered thiol‐ene “click reaction” is carried out, forming the network. It is shown that the network prepared by this approach presents superior adhesion due to greater backbone length, a controlled crosslinking motif, and better‐defined microphase separation. Additionally, the adhesives made by this strategy are thermo‐switchable due to the temperature‐triggered base‐catalyzed thioether dynamic covalent character at 200 °C. Despite providing superior adhesive properties, the proposed technology endows scalable, thermo‐switchable, and O₂‐resistant adhesives with huge industrialization potential.

In this study, we demonstrate that vanillin is a valuable source of aromaticity that can be explored for poly(hydroxy urethane) production with competitive properties, avoiding the use of oil-based or hazardous precursors.

Dynamic urea bond‐mediated polymerization (DUBMP) has been employed for the synthesis of linear, branched, telechelic, and random‐block polyurethanes (PUs) with low molar‐mass dispersity relative to conventionally synthesized PUs (Đ < 1.5). However, the reason for the improved control of the molar mass and reduction in dispersity, promoted by DUBMP, has not been explained. In this paper, the DUBMP synthesis of linear PU based on low‐molar‐mass poly(ethylene glycol) (PEG) and isophorone diisocyanate is studied comprehensively. The lower viscosity of the PEG‐based PU allows DUBMP to reach high conversions (≈0.97) for the first time, while molar mass and Đ vary substantially with reaction conditions, despite yielding similar/equal conversion values. Both molar mass and Đ increase with an increase in reaction temperature, or with a reduction of the amine/isocyanate molar ratio. Therefore, evidence suggests that DUBMP provides diffusion control due to the lower mobility of the longer chains associated with an isocyanate‐deactivator‐rich environment. An increase in the reaction temperature, and/or a decrease in the amine/isocyanate molar ratio, reduces the diffusion control, leading to higher Đ values and molar mass. Tuning of the reaction conditions allows obtaining PU of controlled molar mass (11 kDa ≤ M_w ≤ 42 kDa) and 1.3 < Đ < 1.75.

Hyperbranched polyurethanes (HPUs) are known for their multifunctionality and versatile properties.