Tuning Interaction Parameters of Thermoplastic Polyurethanes in a Binary Solvent To Achieve Precise Control over Microphase Separation

Abstract

Thermoplastic polyurethanes (TPUs) are designed using a large variety of basic building blocks but are only synthesized in a limited number of solvent systems. Understanding the behavior of the copolymers in a selected solvent system is of particular interest to tune the intricate balance of microphase separation/mixing, which is the key mechanism behind the structure formation in TPUs. Here, we present a computationally efficient approach for selecting TPU building blocks and solvents based on their Flory–Huggins interaction parameters for a precise control over the microphase separation/mixing. We first cluster eight soft segments (PEO, PPO, PTMO, PBA, PCL, PDMS, PIB, or PEB) used frequently in TPUs into three categories according to the strength of their interactions with the binary solvent THF/DMF. We then perform a comprehensive set of dissipative particle dynamics simulations of the TPUs in a range of solvent ratios. This enables us to demonstrate the emergence of the unusual channel-like structures in a narrow range of parameters and to determine the critical interactions operative for obtaining either microphase separated or mixed structures. The findings are supported by thermodynamic arguments. The approach developed here is useful for designing novel TPUs with well-defined conformational characteristics, controlled morphologies, and advanced functional properties.

A Celebration of Women in Computational Chemistry

“…The approach developed here is useful for designing novel TPUs with well-defined conformational characteristics, controlled morphologies, and advanced functional properties. 72 While almost all of the accepted papers are on scientific applications of or methods related to computational chemistry, this issue also includes a perspective that provides a glimpse of five computational chemists, led by Georgia McGaughey at Vertex, who ventured into research and development work in the pharmaceutical industry. The authors share their experiences, inspiration, achievements, and contributions in taking compounds to the clinical stage and market.…”

“…Interaction parameters are derived in a bottom-up fashion from atomistic MD and findings are supported by thermodynamic arguments. The approach developed here is useful for designing novel TPUs with well-defined conformational characteristics, controlled morphologies, and advanced functional properties …”

A method to essentially increase the compatibility of thermoplastic polyurethane/methyl vinyl silicone rubber based thermoplastic vulcanizate

“…Moreover, the thermodynamic incompatibility between the hard segment (HS, dibasic isocyanate and glycol) and soft segment (SS, low molecular weight glycol) that constitute TPU also leads to microphase separation. And they then gather to form a hard segment domain (HD) and a soft segment domain (SD) 12 . The fundamental difference between these two‐phase separations lies in the different sizes of the formed phases: the phase separation in TPV is on the order of micrometers, while the microphase separation in TPU is on the order of nanometers 13 .…”

Effect of surface modification of colloidal silica nanoparticles on the rigid amorphous fraction and mechanical properties of amorphous polyurethane–urea–silica nanocomposites

“…The HSs, which consist of hydrogen bonded urethane and/or urea groups formed by the reaction of a diisocyanate with a diol or diamine chain extender, serve as stiff physical cross‐links whose dissociation temperature ( T g or T m ) is typically well above room temperature. Soft segments (SSs), on the other hand, constitute the bulk phase, and their glass transition temperature ( T g ) may be well below the room temperature, resulting in an elastomeric bulk response . The wide range of commercially available starting materials with a correspondingly wide range of compositional and structural features offer considerable design flexibility, and, hence, the synthesis of PUs with controlled morphologies and functional properties.…”

“…However, this also means that there are many different parameters that must be controlled during design, synthesis and processing. The most important of these are: (a) the chemical composition, aromaticity, symmetry, size and length distribution, hydrogen bond strength, and weight/volume fraction of the HS; (b) the chemical structure, end‐group functionality, average chain length (molecular weight), polarity, solubility (typically characterized in terms of the Hildebrand solubility parameter), and weight/volume fraction of the SS; (c) the miscibility of the HS and SS, and the nature and extent of specific intermolecular interactions (principally HS–HS and/or HS–SS hydrogen bonding); and (d) the polymerization procedure, reaction conditions, and processing protocols . The influence of these parameters on the structure–property relationships in PUs has been intensely studied over the years.…”