Host poly electrolyte

Polymer gels and ionomers. Another class of polymer electrolytes are those in which the ion transport is conditioned by the presence of a low-molecular-weight solvent in the polymer. The most simple case is the so-called gel polymer electrolyte, in which the intrinsically insulating polymer (agar, poly(vinylchloride), poly(vinylidene fluoride), etc.) is swollen with an aqueous or aprotic liquid electrolyte solution. The polymer host acts here only as a passive support of the liquid electrolyte solution, i.e. ions are transported essentially in a liquid medium. Swelling of the polymer by the solvent is described by the volume fraction of the pure polymer in the gel (Fp). The diffusion coefficient of ions in the gel (Dp) is related to that in the pure solvent (D0) according to the equation ... 

Poly(ethylene oxide) (usually abbreviated to PEO) has been the most intensively studied host polymer for polymer electrolytes and it serves as a prototype for the structural features in most of the more advanced polymer electrolyte hosts. It consists of —O—CHj—CHj— repeat units and occurs as a semicrystalline solid. The relative orientations of groups... 

The hyperbranched poly( acrylic acid) graft films -C02H-rich interface on polyethylene can be modified by noncovalent methods just like CO2H-rich interfaces of PAA/Au grafts. This was shown by treating deprotonated 3-PAA/PE films with cationic polyelectrolytes like poly-D-lysine, and amine terminated PAMAM dendrimers at pH 7 [31]. Equation 10 illustrates the entrapment of PAMAM dendrimers in a 3-poly(sodium acrylate)/PE film. In these cases, polyvalent entrapment of the cationic electrolyte was evidenced in the ATR-IR spectriun by the appearance of amide C = O and N - H peaks of the guest dendrimer that were not present in the host 3-poly(sodium acrylate)/PE film. 

Typical polymer hosts have Lewis-base sites and include the simple linear polymers PEO, PPO, and poly(ethyleneimine), and a munber of comb polymers, in which oligoether side chains are built on a flexible backbone. A tremendous variety of polymer electrolytes can be prepared. Not only can the anion and cation of the salt be varied, but a wide range of polar polymers that might be suitable hosts for salts can be envisioned. 

There have been reports on the use of polyacrylates and itaconates [166-173] as hosts for polymer electrolytes. Table 7 summarizes the conductivity data observed for these systems. Most of these show conductivities of about 10 5 S cnr1 only at high temperatures. Tsuchida and coworkers have investigated poly [(co-carboxy)] oligo (oxyethylene) methacrylate with an immobilized anion (COO ) as a host... 

In order to appreciate the utility of appropriately substituted poly(phosphazenes) as hosts in polymer electrolytes it is essential to obtain a preliminary idea about the nature of bonding in these polymers [179,181,185,186]. 

The backbone conformational flexibility of poly(phosphazenes) is important for ionic mobility and hence suitably substituted poly(phosphazenes) have attracted considerable interest as hosts in polymer electrolytes. 

In view of the low Tg values normally exhibited by poly (siloxanes), several modified forms of these polymers have been tried as hosts in polymer electrolytes [223-228]. The polymers investigated include block copolymers consisting of... 

Using a similar synthetic methodology, other water soluble polymers, such as poly(vinylpyrrolidinone) (PVP), polyfpropylene glycol) (PPG), and methyl cellulose (MCel) were intercalated into V20s.nH20 xerogels [41]. The ratio of intercalated polymer to the layered host could be synthetically manipulated. Similarly to PEO, PVP, PPG, and MCel could also function as solid electrolytes when complexed with lithium salts, and hence their relevance in lithium battery applications. The intercalation of PEO into V20snH20 was also reported by Ruiz-Hitzky et al. [42]. 

Case Study III - 2,2 -Bipyridine (2,2 -BI on Au(hld) 2,2 -bipyridine is a bidentate ligand used in coordination chemistry and a typical representative of aromatic, nitrogen-containing heterocycles, which act as basic building blocks in highly specific and functionalized host lattices at defined surfaces [548, 549]. Two planar pyridine rings are connected via a C—C bond with 10% double-bond character [550]. Electrochemical studies revealed that n, n -bipyridine [551-553] and several of its Co " " and Ni " " complexes [554] form 2D condensed films at the atomically smooth mercury-electrolyte interface. The adsorption of 2,2 -bipyridine on solid electrodes, such as Ag(poly), Au(hkl), and Cu(lll) was studied by... 

Due to environmental concerns, there has been growing interest in the development of environmental-friendly polymer hosts made from natural sources such as com starch [895,896] and chitosan [734,897] or biodegradable materials such as poly(epsilon-caprolactone) [898] for solid-state electrolytes of ESs. Since the mechanical strength of natural polymers such as starch film was generally low, several studies reported the use of blended materials made from chitosan and starch [897] or chitosan and PEG [734]. 

We have reviewed safety improvements of organic electrolytes by adding flame retardants, and ILs have also been discussed. A more radical solution would be replacing liquid organic electrolytes with solvent-free lithium conductive-membranes reviewed in [196,197]. The most promising options have been briefly reviewed in [198], in particular membranes based on homopolymers, such as poly(ethylene oxide) hosting a lithium salt. However, the conductivity of these polymers is still too low to make them suitable to batteries operating at ambient temperature [199]. 

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