Elucidating the Feature of Intermediate Water in Hydrated Poly(ω-methoxyalkyl acrylate)s by Molecular Dynamics Simulation and Differential Scanning Calorimetry Measurement

Abstract

Intermediate water (IW) has been reported to play an important role in nonthrombogenicity of biomaterials. However, clear insights into the IW in the hydrated polymer are still debated. In this study, a series of molecular dynamics simulations was performed to identify the IW structure in hydrated poly­(ω-methoxyalkyl acrylate)­s (PMCxAs, where x indicates the number of methylene carbons) with x = 1–6. Through the quantitative comparison with experimental measurements, IW molecules were suggested to mainly come from the water interacting with an oxygen atom of the polymers, while most of the nonfreezing water (NFW) molecules corresponded to the water interacting with two polymer oxygen atoms. In addition, the IW molecules were found to effectively enhance the flexibility of the PMCxA side chains in comparison with the NFW molecules. The variations of the saturated IW content and the side-chain flexibility with the methylene carbon chain length of PMCxA were also found to be correlated with the experimental nonthrombogenicity of PMCxA, suggesting that the polymer with the more saturated IW content and higher chain flexibility possesses better nonthrombogenicity. Furthermore, through the analyses of the interplays between the IW and polymer and between IW and its adjacent water, we found that the presence of the unique interaction between IW and its adjacent water in the hydrated poly­(2-methoxyethyl acrylate) (PMEA) is the main factor causing different cold crystallization behaviors of PMEA from the other PMCxAs rather than the interaction between water and the PMCxA matrix. The findings will be useful in the development of new nonthrombogenic materials.

Molecular Dynamics Study on the Water Mobility and Side-Chain Flexibility of Hydrated Poly(ω-methoxyalkyl acrylate)s

“…In a previous experimental study of poly­(ω-methoxyalkyl acrylate)­s (PMC x A, where x indicates the number of methylene carbons in-between ester and ether oxygens of the side-chain) (Figure ), the amounts of adhered platelet and adsorbed fibrinogen on the PMC x A surface have been found to roughly increase with the increase of the side-chain length from x = 2 to 6 because of the decrease in the IW content and increase in the hydrophobicity; however, the conformational change of the adsorbed fibrinogen was suppressed . We have applied MD simulations to investigate the IW structure in the hydrated PMC x A and found that the IW molecules mainly come from BW1 . In addition, the BW1 content of PMC x A was found to decrease with the increase of the side-chain length from x = 2 to 6 .…”

“…In this work, the bound water (BW) is defined as the water interacting with polymer oxygen through the hydrogen (H) bonding following our previous study. , The H bond is defined by referring to geometric criteria among all possible acceptors, donors, and hydrogen atoms. , We assume that the H bond is formed when the distance between an acceptor and a donor is smaller than 0.35 nm and the angle formed by the hydrogen, donor, and acceptor atoms is less than 30°.…”

“…IW and NFW of the hydrated PMEA have been found to interact with the methoxy moiety (O–CH 3 ) and the carbonyl (CO) group, respectively, and their corresponding NMR correlation times are 10 –10 to 10 –9 and 10 –8 to 10 –6 s (Table ). Recently, molecular dynamics (MD) simulations have been applied to distinguish the IW and NFW molecules in the hydrated PMEA. , Instead of the water interacting with specific functional groups, MD simulations identified that IW molecules are mainly categorized as the water interacting with one polymer oxygen atom (named one-bound water, BW1), and most of the NFW molecules correspond to the water interacting with two polymer oxygen atoms (named two-bound water, BW2) (Table ). …”

“…We have applied MD simulations to investigate the IW structure in the hydrated PMC x A and found that the IW molecules mainly come from BW1 . In addition, the BW1 content of PMC x A was found to decrease with the increase of the side-chain length from x = 2 to 6 . It correlated with the experimentally observed amounts of adhered platelet and adsorbed fibrinogen on the PMC x A surface, which roughly increased with the increase of x from 2 to 6.…”

Inhibition of Silica Nanoparticle Adhesion to Poly(vinyl alcohol) Surfaces by Ammonia-Mediated Hydration: Implications for Effective Post-Chemical–Mechanical Planarization Cleaning

“…The arguments here are consistent with recent studies on the anti-fouling mechanism of polymer surfaces. [49][50][51][52] In these studies, water at a polymer-water interface is classified into three categories: nonfreezing water, intermediate water, and free water. Nonfreezing water is tightly bound to a surface and noncrystallizable even at −100 • C. Intermediate water is loosely bound to a surface and crystallizes below 0 • C. Free water is scarcely bound to a surface and crystalizes at 0 • C. Among them, intermediate water is considered to play a key role in the anti-fouling mechanism of a polymer surface.…”