The article "Reversible Polymers from Self-Complementary Monomers, Using Quadruple Hydrogen Bonding" by Sijbesma et al. (1997) introduces a novel approach to creating reversible polymers using self-complementary monomers with quadruple hydrogen bonding. The key findings include: 1. **Monomer Design**: The authors used units of 2-ureido-4-pyrimidone that strongly dimerize in a self-complementary array of four cooperative hydrogen bonds. This design ensures unidirectional binding, preventing uncontrolled multidirectional association or gelation. 2. **Linear Polymers and Networks**: Linear polymers and reversible networks were formed from monomers with two and three binding sites, respectively. The thermal and environmental control over the lifetime and bond strength allows for tunable properties such as viscosity, chain length, and composition. 3. **Viscosity and Concentration Dependence**: Viscosity measurements in chloroform solutions showed concentration-dependent behavior, with compounds 2a and 2b exhibiting different concentration dependencies. NMR studies confirmed the equilibrium between linear polymeric and oligomeric cyclic structures. 4. **Chain Stopper Experiment**: The addition of monofunctional compound 1, which acts as a chain stopper, significantly reduced the viscosity and controlled the degree of polymerization, demonstrating the reversibility of the association process. 5. **Mechanical Properties**: Compound 6, with siloxane spacers, exhibited shear-thinning and polymer-like viscoelastic behavior, with a zero-shear viscosity 1000 times higher than its Newtonian precursor. The thermoplastic behavior of 6 is unprecedented for self-assembled structures. 6. **Reversible Networks**: Reversible polymer networks were obtained from trifunctional copolymers of propylene oxide and ethylene oxide, showing a plateau modulus six times higher than covalently cross-linked copolymers. The reversibility of hydrogen bonds allows for a more dense, thermodynamically determined network. The unique features of these polymers, including high association constants and directionality, enable the creation of polymer networks with thermodynamically controlled architectures, making them suitable for applications in hot melts and coatings where reversible, temperature-dependent rheology is advantageous.The article "Reversible Polymers from Self-Complementary Monomers, Using Quadruple Hydrogen Bonding" by Sijbesma et al. (1997) introduces a novel approach to creating reversible polymers using self-complementary monomers with quadruple hydrogen bonding. The key findings include: 1. **Monomer Design**: The authors used units of 2-ureido-4-pyrimidone that strongly dimerize in a self-complementary array of four cooperative hydrogen bonds. This design ensures unidirectional binding, preventing uncontrolled multidirectional association or gelation. 2. **Linear Polymers and Networks**: Linear polymers and reversible networks were formed from monomers with two and three binding sites, respectively. The thermal and environmental control over the lifetime and bond strength allows for tunable properties such as viscosity, chain length, and composition. 3. **Viscosity and Concentration Dependence**: Viscosity measurements in chloroform solutions showed concentration-dependent behavior, with compounds 2a and 2b exhibiting different concentration dependencies. NMR studies confirmed the equilibrium between linear polymeric and oligomeric cyclic structures. 4. **Chain Stopper Experiment**: The addition of monofunctional compound 1, which acts as a chain stopper, significantly reduced the viscosity and controlled the degree of polymerization, demonstrating the reversibility of the association process. 5. **Mechanical Properties**: Compound 6, with siloxane spacers, exhibited shear-thinning and polymer-like viscoelastic behavior, with a zero-shear viscosity 1000 times higher than its Newtonian precursor. The thermoplastic behavior of 6 is unprecedented for self-assembled structures. 6. **Reversible Networks**: Reversible polymer networks were obtained from trifunctional copolymers of propylene oxide and ethylene oxide, showing a plateau modulus six times higher than covalently cross-linked copolymers. The reversibility of hydrogen bonds allows for a more dense, thermodynamically determined network. The unique features of these polymers, including high association constants and directionality, enable the creation of polymer networks with thermodynamically controlled architectures, making them suitable for applications in hot melts and coatings where reversible, temperature-dependent rheology is advantageous.