Side chain plasticizer effects

Based on their thermal properties, polymeric and glassy molecular PR materials can be classified as high-7 and low-7), materials. The Tg values of polymer composites can be lowered by doping small molecules as plasticizer. Introduction of a long alkyl side chain can effectively reduce the Tg of fully functionalized polymers. The glassy molecular materials usually possess low Tg if they are amorphous. For the high-7 and low-7), materials, the figures of merit of the NLO chromophores are defined by Eqs. (35) and (40), respectively. The latter are obviously enhanced by contributions from the polarizability anisotropy of the NLO chromophore. 

A HE SEARCH FOR PLASTIC, solvent-free electrolytes for use in solid-state batteries is being actively pursued in several laboratories (1-4). A number of reports have stressed the need for facile motion of the macromolecular chain in order to promote the ion conduction process in the polymer matrix, because this process occurs primarily via a free-volume mechanism (1-4). Comblike polymers with oligooxyethylene side chains constitute effective media for ion conduction of solubilized alkali salts (5-8). The low glass transition temperature (Tg) of poly(dimethylsiloxane) suggests that polysi-loxane could serve as a suitable backbone for such a comb polymer, and recent studies (9-J2) indicate this to be the case indeed. 

The increase in the length of the side chain results normally in an internal plasticization effect caused by a lower polarity of the main chain and an increase in the configurational entropy. Both effects result in a lower activation energy of segmental motion and consequently a lower glass transition temperature. The modification of PPO with myristoyl chloride offers the best example. No side chain crystallization was detected by DSC for these polymers. 

In a subsequent communication, Elliott and coworkers found that uniaxially oriented membranes swollen with ethanol/water mixtures could relax back to an almost isotropic state. In contrast, morphological relaxation was not observed for membranes swollen in water alone. While this relaxation behavior was attributed to the plasticization effect of ethanol on the fluorocarbon matrix of Nafion, no evidence of interaction between ethanol and the fluorocarbon backbone is presented. In light of the previous thermal relaxation studies of Moore and co-workers, an alternative explanation for this solvent induced relaxation may be that ethanol is more effective than water in weakening the electrostatic interactions and mobilizing the side chain elements. Clearly, a more detailed analysis of this phenomenon involving a dynamic mechanical and/ or spectroscopic analysis is needed to gain a detailed molecular level understanding of this relaxation process. 

In summary, our studies have show n that graft copolymers of PVN with PEO form homogeneous, rubbery materials. The properties of copolymers having low PEO content remain to be investigated to evaluate the use of PEO as an internal plasticizer. Also, the effect of the size of side chains will have to be considered. 

In dicyanocobalt(III) a,b,c,d,e,g-hexamethyl-f-stearylamide cobyrinate (derivative 3) the six peripheral amide groups of vitamin B12 have been replaced with methyl ester groups, and the proximal base of the vitamin at the f-position with a stearylamide group (11). Electrodes prepared with this ionophore and DOS as the plasticizer were also selective for thiocyanate and nitrite over the rest of the anions tested. The main anionic interferent was salicylate. In all cases, the response of the electrodes to the preferred anions was sub-Nemstian. Overall, the selectivity pattern obtained with ionophore 3 is similar to that of 2 and to that of the hydrophobic cobyrinate-based electrodes reported previously (5, 12, 13). This observation suggests that in all cobyrinate ionophores the anions interact with the cobalt(III) center, and that the side chains of the corrin ring have a small effect on the selectivity of this interaction. 

Methylene (-CH2-) units in side groups generally cause "internal plasticization" and lower Tg. The only common exceptions to this rule are hydrocarbon polymers with very long side chains, where side chain crystallization and/or other nonbonded interactions between side groups may counter this effect, and cause a slight increase of Tg with increasing number of methylene units after a certain side chain length is exceeded. 

The heat of polymerization of vinyl esters exhibits essentially no dependence on the length of the carboxylic acid. Generally the range of the heats of polymerization is between 20.5 and 21 kcal/mole. Steric strain is thought to reduce this value in the case of vinyl benzoate and the plasticizing effect of the side chains is believed to raise the value slightly in the case of vinyl 2-ethylhex-anoate [17,18],... 

It is generally observed that as longer spacer units are introduced, the Tg of the polymer is lowered by internal plasticization and the tendency for the more ordered smectic phase to develop is increased. A similar ordering effect is also encouraged by lengthening the alkyl tail unit (see Table 5.7). Both these phenomena reflect the known tendency for long side chain to order and eventually to crystallize, when sufficiently long, and this condition persists also in the liquid crystal state. 

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