# Preparation and Chemical Protective Clothing Application of PVDF Based Sodium Sulfonate Membrane
## 1 Introduction  
Nerve agents are the most toxic class of chemical warfare agents (CWAs), including tabun (GA), sarin (GB), soman (GD), and VX as representatives (Figure 1). These agents are usually colorless, odorless, and highly toxic. Vapor permeation is the primary route of exposure to nerve agents, which can cause immediate damage after exposure to small amounts of nerve agents vapor [1]. Sulfur mustard, one of the most famous CWAs introduced in World War I, can easily permeate the human skin and alkylate the DNA to cause cell death. Sulfur mustard as the representative of blister agents has been widely used in many wars during the last century and caused thousands of deaths [2]. Therefore, it is crucial to develop chemical protective clothing (CPC) to protect people from exposure to CWAs vapors. In the initial stage, researchers use simulants to study and evaluate the protective performance against nerve agents. The most commonly used simulants are dimethyl methyl phophonate (DMMP) for nerve agents and 2-chloroethyl phenyl sulfide (CEPS) for blister agents (Figure 1). Rubbery barrier materials have been previously demonstrated as effective CPC materials against CWAs [3; 4; 5]. However, the transfer of water vapor was blocked at the same time, resulting in heat stress and faint for the users [6]. On the other hand, adsorptive fabrics with activated carbon adsorbent have also been used to adsorb chemical warfare agents [7; 8]. Although better physiological comfort could be achieved, there still exist defects, such as limited sorbent capacity, high weight, and secondary contamination caused by desorption [9]. Ideally, the protective material should work selectively, which transports water and blocks water-soluble toxic compounds. Polyelectrolyte membranes (PEMs) composed of hydrophobic and hydrophilic segments may be used to resolve this apparent contradiction. The self-assembly of a PEM upon solvation can form a permselective network containing nanoscale hydrophilic channels. Typical examples of such selective permeable membranes are sulfonated poly(styrene-isobutylene-styrene) (SIBS), triblock copolymer, perfluorinated ionomers, and polystyrene sulfonic acid (PSSA) [10; 11; 12; 13; 14; 15; 16; 17; 18; 19]. However, sulfonated SIBS has poor selectivity between 0.7 and 35 [19]. Nafion is too expensive for chemical protective clothing usage ($1600 m\({}^{-2}\) for Nafion 117) [20], and polystyrene sulfonic acid has a poor mechanical performance [14]. As for the selectivity of the membrane, [PERSON] et al. systematically studied the water/DMMP selectivity of a SIBS-based ion exchange membrane under different degrees of sulfonation [18; 19]. By using classical molecular dynamics simulations, [PERSON] et al. explored the nanoscale segregation and diffusion of water and nerve gas simulant DMMP in sulfonated polystyrene (sPS) at different sulfonation and hydration levels. The result suggests that sPS is permeable for both DMMP and water. However, DMMP molecules partially segregated on the scale of 1-2 nm and have different pathways through the system [15]. Therefore, a new membrane design concept for CPC application, and deepening understanding of the relationship between membrane structure and selective transport properties, is desirable. Building on recent advances with ion-exchange membranes, modification based on existing commercial high-performance polymers can reduce costs and obtain excellent and stable membrane  
Figure 1: Common CWAs and their simulants. performances. Polyvinylidene chloride (PVDC) is well known as an ideal packaging material with high barrier properties, strong toughness, excellent chemical stability, and low thermal shrinkage. Notably, it has a high tolerance to acid, alkali, oil immersion, and various chemical solvents [21; 22]. However, its low-temperature solubility, poor compatibility with hydrophilic additives limit its wide application for CPC.