Energetic Characteristics

Increasing reaction temperature usually increases the polymerization rate. Quantitative relationship between polymerization rate and temperature. 

A composite or overall activation energy for the rate of polymerization. 

All values are for 50 C unless otherwise noted. Source Data from Ref. 3. 

From the slope and intercept of the linear plot of lni p versus l/T we can determine Erp and Ap Ad / AtY. For most monomers, Ep and Et are in the range 5-10 kcal/mol and 2-5 kcal/mol, respectively, while for most initiators commonly used in thermal homolysis Ed is in the range 

30-35 kcal/mol. Therefore, i/Rp is about 20 kcal/mol. A temperature rise of 10°C will thus cause a two- or three-fold increase in the rate of polymerization. For redox initiation, however, Ed —10-15 kcal/mol and so Epp 10 kcal/mol which is one-half the value for nonredox initiators. In photo-initiation, on the other hand, the energy for the dissociation of the initiator is supplied by the radiation quanta the initiation is therefore independent of temperature and hence Ed = 0. From Eq. (6.181), Ep,p Ci5 kca]/mol. This low value of activation energy signifies that the polymerization rate in photo-initiated systems is relatively insensitive to temperature. 

Temperature (°C) Intrinsic Viscosity of Polymer (dL g-1) Ultimate Conversion of Monomer (%) Proportion of Tetramer (%) 

3- dioxolane, oxepane, and 1,3-dioxepane, respectively [Chien et al., 1988 Dreyfuss and Dreyfuss, 1976 Sims, 1966]. The ERp value is 72 kJ mol-1 for 3,3-his(chloromethyl)oxetane [Chapiro and Penczek, 1962 Penczek and Penczek, 1963]. As with ionic polymerizations of alkenes, the activation energies can vary considerably with reaction conditions. Thus ERp for 

3- bis(chloromethyl)oxetane is only 12-16 kJ mol-1 for radiation-initiated polymerization in the crystalline state. The lower activation energy may be a consequence of a favorable orientation of the monomer for propagation in the crystalline state. 

---

Energetic characteristics for some of the compounds of interest are listed in the following Table. 

In addition, detailed geometric and energetic characteristics of the elementary reaction pathways for the addition of water and ammonia to 2-methyl-5(477)-oxazolone have been determined at the AMI level using MOPAC programs. The authors concluded that an A-acetylamino acid or amide are formed through a two-step procedure that involves the formation of the a-hydroxyimine and subsequent tautomerization. 

Table 13 Energetic characteristics of a range of [1,2,3]triazoio[4,5-c][1,2,5]oxadiazoiium inner salts...

The thin control of the energetic characteristics and the electronic transition nature may be carried out by chemical structure alteration. For example the appearance of CH2 group between phenyl ring and triple bond (compounds 3 and 5 in Table 4) interrupts the interaction between it-ekctrons of the both elements. This leads to the short wavelength shift in the absorption and photoconductivity spectra. The insertion of the ethynyl group instead of a CH2 group restores the conjugation. The increase in the numbers and sizes of the... 

Figure 1 3 1. Energetic characteristics of a model cuprate on the doping scale. 1 - the underdoped state small pseudogap As 2 - the large pseudogap A, 3 - the defect system superconducting gap Aa 4 - the itinerant system superconducting gap Ay 5 - Tc. The insert shows normal state gaps. p = 0.18 Pp- 0.12 0 0.23 p(Tcm) = 0.23]...

The present simple and partly postulative model seems to be able to reproduce the observed behaviour of the cuprate energetic characteristics. The possible coexistence of pseudogap with the superconducting gap of the other partner subsystem has been demonstrated. The transformation of the... 

The majority of results obtained by theoretical methods are treated in more detail in appropriate sections of this chapter. We will dwell here briefly on the applicability of various quantum-chemical methods to the description of the tetrazole ring structure and its energetic characteristics. 

Reference data on total energies of forms 19-23 optimized by means of different theoretical methods in the gas phase are given in Table 2. Various energetic characteristics of tetrazoles can be successfully estimated. The vertical adiabatic ionization potentials of both neutral tautomers 20 and 21 were calculated for a- and Tt-radical cations <2000CPL(330)212>. The standard molar thermodynamic functions (enthalpies, heat capacities, and entropies) of... 

Fig. 14 Schematic view of the association between morphological arrangements of carbon crystallites and energetic characteristics of carbon black surfaces. Four different types of adsorption sites are distinguished that refer to the de-convolution shown in Fig. 13...

Results of Calculations (CTP, CNDO/BW) of the Energetic Characteristics for Different Forms of Water Molecule Adsorption on Acid-Base Sites of H Forms of Zeolites as a Function of the Strength of the Acid site"... 

A typical problem resolved through correlation ratios is identifying the conditions of the maximal catalyst activity—that is, to optimize the catalyst properties at changes in energetic characteristics of catalytic intermediates due to, for example, variations in the energy of their bonding to the active... 

Of course, the present simple computer experiment caimot be considered as an exact counterpart of the ice melting because liquid water cannot be topologically related to ice by the simple breaking of the H-bonds of the latter. Indeed, our computer experiments deal only with energetic characteristics of the ice melting and do not account for changes in entropy and volume. However, the obtained results can be helpful in analyzing various liquid water models. 

Meaningful results regarding the structural and energetic characteristics of methanol/water mixtures were obtained by... 

---