Segmental mobility dynamics

C relaxation experiments are useful in studying the molecular motions of crown ethers and cryptands. Uncomplexed dibenzo[18]crown-6 shows a segmental mobility which disappears on complexation. Similarly, alkyldiammonium salts have shorter relaxation times when complexed by large cylindrical cryptands (Figure 15). The dynamic coupling of the molecular motions of substrate and receptor increases with their structural complementarity in the complex (81CC833). 

Table III also shows that E increases with increasing DSC T. This would be expected from restricted segmental mobility of trie high T samples. Lewis iH found that Arrhenius plots of log frequency versus reciprocal dynamic glass transition temperature for restricted and nonrestricted polymers converges to a different point in the frequency/temperature scale. From this finding, equations were derived to predict static T from the dynamic T value and vice versa. ...

It now appears that the dissolution dynamics of glassy polymers is at the very least a complicated process and its kinetics depends on many parameters of the solvent, the polymer and the processing condition. We have also found that one of the dynamical processes that strongly affect the dissolution kinetics of polymers with high Tg is the diffusion rate of the solvent into the polymer matrix which primarily depend on at least 4 factors polymer free volume and segmental mobility, solvent size and the osmotic pressure (chemical potential difference between the polymer solution and pure solvent). We believe that the above finding has important implication in resist technology. Positive... 

It is assumed that the limited proteolysis phenomenon derives from the fact that a specific polypeptide chain segment of the compact, folded protein substrate is exposed and flexible so that it can fit the active site of the appropriate peptidase for an efficient and selective limited hydrolysis. There is no doubt that enhanced chain flexibility or segment mobility is the key feature of the site of peptide bond hydrolysis demonstrated by a clear-cut correlation between sites of proteolytic attack and sites of enhanced chain flexibility. The present availability of automatic, efficient and sensitive techniques of protein sequencing and, particularly, the recent dramatic advances of mass spectrometry 361 in the analysis of peptides and proteins, allows a more systematic use of the limited proteolysis approach as a simple first step in the elucidation of structure-dynamics-function relationships for novel proteins which are only available in minute amounts. 

Mechanical Properties Chen et al. [2007] smdied the dynamic mechanical properties of films prepared by the solution casting method of PHBHV reinforced with HAp. The results indicated that at 75°C the storage tensile modulus of the polymer matrix, E , almost doubled by incorporation of 30 wt% HAp. The decrease in tan S was attributed to the hindrance of polymeric segment mobility by the nanofiller. Polyamide-69 has been reinforced with up to 10 wt% HAp [Sender et al., 2007]. The DMA results have pointed out an enhancement of the mechanical properties as a function of HAp content up to 5 wt% above this limit they deteriorated, probably due to the HAp agglomeration. 

Static and dynamic glass transition temperatures can be interconverted. The probability p of segmental mobility increases as the free-volume fraction /wi.F increases (see also Section 5.6.1). For/wlf = 0, of necessity, p = 0. For /wLF it follows thatp =. The functionality is consequently... 

The extent of segmental mobility also affects die modulated miisolropy (r ) data. The values of at low modulation frequency reflect the steady-state anisotropy and are thus lower for the proteins with higdio segmental flexibility. The transition of toward the hifdi-frequency value of ro occurs at higher frequency for proteins with greater flexibility. It is apparent from these data that the FD anisotropy data are highly sensitive to the form of the anisotropy decay and/or the dynamic properties of the proteiiis. 

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