Ladder macromolecule

Macromolecule consisting of an uninterrupted sequence of rings with adjacent rings having one atom in common (spiro macromolecule) or two or more atoms in common (ladder macromolecule). 

Note A ladder macromolecule is a double-strand macromolecule with adjacent constitutional units joined to each other through four atoms, two on one side and two on the other side of each constitutional unit. 

Note 2 A polymer, the macromolecules of which are ladder macromolecules, is termed a ladder polymer. 

The polyalumophenylsiloxane obtained is a polydisperse mixture of polymer homologues consisting of the abovementioned ladder macromolecules and branched macromolecules of the following common formula [C6H5Si(OH)2.xO0.5x(O)]3AI n... 

An alternative approach would generate precursor macromolecules with some disorder of the rigid geometry. A possible way of achieving this is the generation of polymers that have structural units which cause an angular shape of the double-stranded chain. Such precursor polymers then have to be converted into the final ladder macromolecules by means of an elimination or rearrangement step [2, 5]. 

In 1993, Scherf and Chmil described the first synthesis of a ladder-type poly(pflra-phenylene-czs-vinylene) (116) [138]. On the one hand, ladder polymer 116 represents, a planar poly(phenylene) containing additional vinylene bridges on the other hand, it is a poly(phenylenevinylene) with aryl-aryl linkages in the polymeric main chain. The target macromolecules, as fully aromatic ladder polymers, are composed of all-carbon six-membered rings in the double-stranded main chain (an example of angularly annelated poly(acene)s). 

S. Setayesh, D. Marsitzky, and K. Mullen, Bridging the gap between polyfluorene and ladder-poly-p-phenylene synthesis and characterization of poly-2,8-indenofluorene, Macromolecules, 33 2016-2020, 2000. 

C. Xu, H. Yamada, A. Wakamiya, S. Yamaguchi, and K. Tamao, Ladder bis-silicon-bridged stilbenes as a new building unit for fluorescent Tr-conjugated polymers, Macromolecules, 37 8978-8983, 2004. 

Ladder polysilanes constitute a special case of fused polycyclic silicon macromolecules, in which cyclotetrasilane rings systematically catenate to form a silicon double helix, comprising two multi-linked silicon chains. Work in this area was initiated in this area by Matsumoto in 1987, and now comprises an integral part of the literature on higher-dimensionality polysilanes. 

We can assume that on average for one macromolecule of product obtained, there are X units with ladder-type structure, Y unreacted groups with double bonds, and Z points of crosslinking. The scheme of copolymerization of multimethacrylate with acrylic acid and a possible structure of the product obtained are presented in Figure 5.2. 

Covalent bonding of acrylic or methacrylic monomer to the template leads to multifunctional monomers (multimonomers).If monomer units are connected by covalent bonds within the frame of the template and polymerization proceeds according to the zip mechanism , a product with ladder-type structure can he expected. The structure of products obtained depends on the competition between the reactions proceeding on the template and the reaction between groups belonging to different macromolecules (templates). Template homopolymerization in this case can he represented by the scheme given in Figure 9.1. 

Template copolymerization seems to be applied to the synthesis of copolymers with unconventional sequences of units. As it was shown, by copolymerization of styrene with oligomers prepared from p-cresyl-formaldehyde resin esterified by methacrylic or acrylic acid - short ladder-type blocks can be introduced to the macromolecule. After hydrolysis, copolymer with blocks of acrylic or methacrylic acid groups can be obtained. Number of groups in the block corresponds to the number of units in oligomeric multimonomer. Such copolymers cannot be obtained by the conventional copolymerization. 

Our treatment of basic principles of water-solute relationships involves a bottom-up approach that begins with a basic physical-chemical analysis of how fundamental water solute interactions have set many of the boundary conditions for the evolution of life. We discuss how the properties of macromolecules and micromolecules alike reflect selection based on such fundamental criteria as the differential solubilities of different organic and inorganic solutes in water, and the effects that these solutes in turn have on water structure these are two closely related issues of vast importance in cellular evolution. With these basic features of water-solute interactions established, we will then be in a position to appreciate more fully why regulation of cellular volume and the composition of the internal milieu demands such precision. We then can move upwards on the reductionist ladder to consider the physiological mechanisms that have evolved to enable cells to defend the appropriate solutions conditions that are fit for the functions of macromolecular systems. This multitiered analysis is intended to help provide answers to three primary questions about the evolution and regulation of the internal milieu ... 

Some representative examples of common zero-temperature VER mechanisms are shown in Fig. 2b-f. Figures 2b,c describe the decay of the lone vibration of a diatomic molecule or the lowest energy vibrations in a polyatomic molecule, termed the doorway vibration (63), since it is the doorway from the intramolecular vibrational ladder to the phonon bath. In Fig. 2b, the excited doorway vibration 2 lies below large molecules or macromolecules. In the language of Equation (4), fluctuating forces of fundamental excitations of the bath at frequency 2 are exerted on the molecule, inducing a spontaneous transition to the vibrational ground state plus excitation of a phonon at Fourier transform of the force-force correlation function at frequency 2, denoted C( 2). 

Investigation of the intermolecular mobility of the individual PMAA and PEG macromolecules by means of the polarized luminescence method confirms the assumption that in PMAA-PEG polymer complexes there exist sequences having a ladder structure. The relaxation times of luminescence-labelled PMAA and PAA macromolecules differ almost by two orders of magnitude. The low intramolecule mobility of PMAA macromolecules in water is caused by their specific conformation namely by the presence of the locally structured segments. The high intramolecular mobility of PEG is induced by its high kinetic flexibility. As seen from Table 1, the relaxation times of separate macromolecules disappear and the relaxation time of the complex is much longer. 

The Diels-Alder-route to ladder polymers is clearly a powerful method for the formation of the primary cycloaddition products. The key problem, however, is the polymer-analogous transformation of the primary macromolecules. 

The above examples of a stepwise synthesis of a ladder polymer involve the formation of single-stranded polymers via polymerization of suitable monomers to functionalized precursors. These consist of substituted poly(ethylene)- or (polyacetelyne)-type macromolecules, from which attempts are made to carry out a defined polymer-analogous cyclization reaction. 

The following example describes the first successful synthesis of a soluble and structurally defined ladder polymer by the stepwise route. It illustrates the synthetic potential of the classical route to ribbon-type macromolecules. 

The synthetic sequence to methylene-bridged poly(phenylene)s 71 represents the first successful employment of the stepwise process to ladder-type macromolecules involving backbone formation and subsequent polymer-analogous cyclization. As shown, however, such a procedure needs carefully tailored monomers and reaction conditions in order to obtain structurally defined materials. The following examples demonstrate that the synthesis of structurally defined double-stranded poly(phenylene)s 71 (LPPP) via a non-concerted process is not just a single achievement, but a versatile new synthetic route to ladder polymers. By replacing the dialkyl-phenylenediboronic acid monomer 68 by an iV-protected diamino-phenylenediboronic acid 83, the open-chain intermediates 84 formed after the initial aryl-aryl cross-coupling can te cyclized to an almost planar ladder-type polymer of structure 85, as shown recently by Tour and coworkers [107]. 

These polymers have been synthesized on the basis of polysiloxane macromolecules with a double chain structure and aromatic and aliphatic side groups " ) (Fig. 2). However, the length of the Kuhn segment for chains with a ladder structure can vary depending on the conditions of the synthesis (Table 2). This means that the defects in the ladder structure may play a certain part in the flexibility of these polymers. Nevertheless, the main mechanism of their flexibility involves the deformation of valence angles and bonds of their double-chain network ... 

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