Macromolecular architecture effect

Protein polymers based on Lys-25 were prepared by recombinant DNA (rDNA) technology and bacterial protein expression. The main advantage of this approach is the ability to directly produce high molecular weight polypeptides of exact amino acid sequence with high fidelity as required for this investigation. In contrast to conventional polymer synthesis, protein biosynthesis proceeds with near-absolute control of macromolecular architecture, i.e., size, composition, sequence, topology, and stereochemistry. Biosynthetic polyfa-amino acids) can be considered as model uniform polymers and may possess unique structures and, hence, materials properties, as a consequence of their sequence specificity [11]. Protein biosynthesis affords an opportunity to completely specify the primary structure of the polypeptide repeat and analyze the effect of sequence and structural uniformity on the properties of the protein network. 

Teyssie and coworkers [86] studied the effect of macromolecular architecture on the lamellar structure of the poly(ethylene oxide) crystallizable arms in (poly tert-butyl styrene)(poly(ethylene oxide))2 [PtBuS(PEO)2] miktoarm stars by using SAXS and differential scanning calorimetry (DSC). The results were compared with the ones obtained on poly(tBuS-fe-EO) materials. At the same total molecular weight and composition the melting temperature, the degree of crystallinity and the number of folds of PEO chains were found to be lower for the branched samples. 

Confinement effects in thin films of hyperbranched polyester show up at thickness much larger than those reported for linear polymers. This must be attributed to their special macromolecular architecture. 

Tests of the light stabilizing activity of monomeric HAS and the corresponding homo- and copolymers reveal mostly better properties of the monomers if physical persistence is not the decisive testing factor [8]. This was found e.g. in comparison of the functionalized urethane 182 and its copolymers with styrene or methyl methacrylate [303], The macromolecular architecture is expressed very distinctly. For example, a PP photografted HAS-functionalized acrylate was more efficient than the respective monomer or homopolymer. Another observation performed with A-(2,2,6,6-tetramethyl-4-piperidyl)methacry-lamide, piperidyl acrylate and methacrylate, their homopolymers and copolymers with dodecyl methacrylate and octadecyl acrylate revealed that the stabilizing effect in PP was in favour of copolymers [304]. Similar HAS-functionalized monomers were copolymerized with styrene. In this case, the copolymers were substantially less efficient in PS than the monomers. Masterbatches of PP-bound HAS prepared by reactive processing imparted a comparable effectivity as conventional HAS when tested at an equimolar basis [298]. 

Escale, P., Ting, S.R.S., Khoukh, A., Rubatat, L., Save, M., Stenzel, M.H., Billon, L. Synthetic route effect on macromolecular architecture from block to gradient copolymers based on acryloyl galactose monomer using RAFT polymerization. Macromolecules 44(15), 5911-5919 (2011)... 

Copolymerization is the most important synthetic strategy available to tailor the physical, solution and mechanical properties of macromolecules. In this paper the synthesis of well defined random and block copolymers containing monomer units of very different polarity are described. Novel macromolecular architectures incorporating 4-hydroxystyrene, t-butylacrylate and styrene have been prepared to investigate the combined effects of macromolecular architecture and hydrophobicity on thin film aqueous base dissolution. 

The dissolution behavior of copolymers in aqueous base is of primary importance in photoresist performance. As microlithography continues to decrease in exposure wavelength and the minimum feature size required from photoresist compositions decreases below 0.20 pm, control of macromolecular architecture will play an increasingly significant role. That is, how does the random, alternating or "blocky nature of the matrix polymer effect its solubility in aqueous base. It has been well documented for novolac based photoresists that the molecular weight distribution... 

Effect of Macromolecular Architecture Upon Aqueous Base Dissolution. To... 

Three-dimensional branched architectures, generally termed dendrimers, represent a class of synthetic macromolecules that have impacted dramatically on the field of organic and polymer chemistry and created a new branch in synthetic and material chemistry. For the last two decades, dendrimer research has been at the forefront of polymer research and was first postulated in the 1940s by Flory, a pioneer in polymer research and Nobel Laureate in 1974, who proved the existence of branched chains and their potential role in three-dimensional (3D) macromolecular architectures [446-448], In 1978, Vogtle et al. developed an iterative cascade method for the synthesis of low molecular weight branched amines [449]. The real expansion of the field started after Tomalia et al. [450] and Newkome et al. [451] discovered the starburst effect, which shed light on a new chemical arena. Since then, dendrimer chemistry has been diversified... 

Very recently, the first examples of hybrid block copolymers comprising in the same macromolecule both main-chain and side-chain LC blocks (7) have also been described. To gain a better insight into the effects of the macromolecular architecture on the phase transition behavior of this last class of block copolymers, in the present contribution we report on the synthesis and properties of three series of main-chain and side-chain LC block copolymers 1-3, characterized by the following general structure ... 

Another question important for the academic community is What type of training should we provide at universities for the polymer scientists which we need at the turn of the century This is essential to provide the proper manpower which can effectively handle delicate design of polymer structures for advanced applications which are based on macro-molecular design, macromolecular architecture, and macromolecular engineering. 

Therefore, a fundamental understanding of solution properties of macromolecules and their assemblies is of cmdal importance for both polymer sdence and technology as well as biology and medicine. There are a number of classical books considering properties of solutions of linear-chain macromole-cules. In this chapter, we aim to make a major emphasis on the effects of macromolecular architecture, that is, topology and amphiphilic nature, on the solution properties of macromolecules. 

Other macromolecular architectures, such as linear polymers, and any comparisons that have been made were performed with polydisperse samples of significantly different repeat unit structure. For example, the unique melt viscosity behavior of polyether dendrimers was compared with linear polystyrene and not with monodisperse linear analogs containing the same number of polyether repeat units based on 3,5-dihydroxybenzyl alcohol (2). Because of this, important issues, such as i) effect of the numerous chain end functional groups, ii) the effect of branching and, iii) the development of a well defined three-dimensional architecture cannot be addressed and the underlying reason for these inherent differences remains a mystery. 

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