Alkyl poly chain length effect

In this chapter, the properties of a series of poly(dimethylsiloxane-co-methylalkylsiloxane) (PDM-PMAS) of various alkyl side-chain lengths are discussed. These polymers contain 3.5 mol % methylalkylsiloxane units and are prepared from the same precursor thus, any effects due to variations in the percentage of alkyl substitution and main-chain molecular weight differences and effects due to block distribution of the alkyl substituents are eliminated. 

Vanderzande, D., Manca, J.V., 2009. Effect of alkyl side-chain length on photovoltaic properties of poly(3-alkylthiophene)/PCBM bulk heterojunctions. Adv. Funct. Mater. 19,3300-3306. 

Sound Speed. A number of studies have been made on the effect of variations in molecular structure on sound speed. Replacing the hydrogen atoms in polyethylene with fluorine atoms lowers the sound speed, in line with the expectation that there will be a reduction in intermolecular attraction due to the larger size of the fluorine atoms (53). In this case, the sound speed also decreases because the polymer density increases. Similarly, in a series of poly(alkyl methacrylates), the sound speed decreases as the alkyl side-chain length increases (84). Again, there is a volume increase that reduces the intermolecular attraction. 

Y. Ohmori, M. Uchida, K. Muro, and K. Yoshino, Effects of alkyl chain lengths and carrier confinement layer on characteristics of poly(3-alkylthiophene) electroluminescent diodes, Solid State Commun., 80 605-608, 1991. 

TX-45, TX-114, TX-100 have the same hydrophobic group (4-(l,l,3,3-tet-ramethylbutyl)phenyl), but have different lengths of hydrophilic poly ethoxy 1 chain, i.e. n = 5, 7.5 and 10, respectively (Scheme 4.6) Tween 20 and Tween 80 have the same molecular structure and EO number, while differentiate in the hydrophobic alkyl chain length. It is well known that the smaller the Henry s constant, the larger the solubility. The Henry s constants of C02 (e.g., 25 °C) in the surfactants with more EO content are smaller (TX-45 39.8 > TX-114 28.7 > TX-100 20.0), while the effect of alkyl chain length on the Henry s constant is very limited (Tween 20 10.7 and Tween 80 10.1). The absolute value of the enthalpy increases considerably with increasing EO content (TX-45 -14.5 2.1, TX-114 -15.9 2.3 and TX-100 -20.4 1.6) [83]. 

Figure 6. Effect of increased alkyl chain length on glucose sensor response glucose calibration curves for the ferrocene-modified poly(siloxane) / glucose oxidase / carbon paste electrodes at E = +300 mV (vs. SCE). The polymeric relay systems are indicated next to each curve, which is the mean result for four electrodes.

Z, the critical chain length, which we have assumed to be absent. These effects are not. of course, mutually exclusive. Some anomalies in the reduction factors for viscoelastic properties noted by Ferry and co-workers (57) for poly(alkyl methacrylates) may be related phenomena. These were interpreted to be a manifestation of the dissociation of coupling points, an effect not observed for other polymers. In a recent study. 

A comparison of poly(3-alkylthiophene)s (P3ATs) with side chains ranging from butyl (35d) to dodecyl (35g) showed a non-monotonic dependence of field-effect mobility on alkyl chain length (Figure 3.1.13).[11,210] The average mobility varied... 

Babel, A. and Jenekhe, S.A., Alkyl chain length dependence of the field-effect carrier mobility in regioregular poly(3-alkylthiophene)s, Synth. Met. 148, 169-173, 2005. 

DEL DeLisi, R., Lazzara, G., Milioto, S., and Muratore, N., Thermodynamics of aqueous poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide)/surfactant mixtures. Effect of the copolymer molecular weight and the snrfactant alkyl chain length,/. Phys. Chem. B, 108, 18214, 2004. 

---