Hexyl side-chains

Structurally, plastomers straddle the property range between elastomers and plastics. Plastomers inherently contain some level of crystallinity due to the predominant monomer in a crystalline sequence within the polymer chains. The most common type of this residual crystallinity is ethylene (for ethylene-predominant plastomers or E-plastomers) or isotactic propylene in meso (or m) sequences (for propylene-predominant plastomers or P-plastomers). Uninterrupted sequences of these monomers crystallize into periodic strucmres, which form crystalline lamellae. Plastomers contain in addition at least one monomer, which interrupts this sequencing of crystalline mers. This may be a monomer too large to fit into the crystal lattice. An example is the incorporation of 1-octene into a polyethylene chain. The residual hexyl side chain provides a site for the dislocation of the periodic structure required for crystals to be formed. Another example would be the incorporation of a stereo error in the insertion of propylene. Thus, a propylene insertion with an r dyad leads similarly to a dislocation in the periodic structure required for the formation of an iPP crystal. In uniformly back-mixed polymerization processes, with a single discrete polymerization catalyst, the incorporation of these intermptions is statistical and controlled by the kinetics of the polymerization process. These statistics are known as reactivity ratios. 

IR and Raman spectroscopic studies on films and powders of PDHS indicate that the hexyl side chains are crystallizing into a hydrocarbon type matrix (40). This is indicated by the presence of a number of sharp characteristic alkane bands which become dramatically broadened above the transition temperature. Similar changes are observed for n-hexane below and above the melting point. CPMAS 29Si NMR studies on PDHS also show that the rotational freedom of the side chains increases markedly above the transition temperature (41,42). All of the spectral evidence... 

A recent study of poly(di-n-hexylsilane) films by V.R. McCrary et al. (17) measured the polarization dependent Cls and Si2p NEXAFS spectra, EXAFS, and UPS as a function of temperature. Above 42°C it was found that the hexyl side chains were disordered and that the Si backbone was partially disordered (no longer an all-trans configuration). Below 42°C there was coexistence of the disordered phase with the well-ordered (all-trans backbone and side chains) phase. 

A more limited study of the solvent dependence of Tc was also performed with poly(di-n-pentylsilylene). Experimental results for three solvents are listed in Table II, and a correlation plot is presented in Figure 3. As was found for poly(di-n-hexylsilylene), an excellent agreement with the theoretically predicted linear dependence was obtained. The steeper slope for the di-n-pentyl polymer is consistent with theoretical expectations, because the pentyl group is smaller than a hexyl side chain and therefore provides less shielding of the polymer backbone from the solvent molecules. 

As seen from the pyrogram and from the pyrolysate composition shown in Table 15.1.4, the main components are generated from the hexyl side chain. Some other pyrolysis... 

Comonomer having hexyl side chain was added to N-vinylpyrrolidone to improve its properties. It was fonnd that the inclusion of comonomer rednces glass transition temperature of copolymer because it acts as an internal plasticizer. Polyimides are internally plasticized with alkyl 3,5-diaminobenzoate compounds. Without internal plasticization a polymer has too high a glass transition temperature that makes processing veiy difficult. 

A series (Scheme 6.10) of dialkyldipropynylbenzenes was exposed to mixtures of Mo(CO)g and 4-chlorophenol in technical grade chlorobenzene, 1,2-dichlorobenzene, or 1,2,4-trichlorobenzene. Clean formation of PPEs was ensured if the formed butyne is swept out by a gentle stream of nitrogen or argon [16,38]. The polymers 4a-e form in quantitative yields as yellow powders after workup and show high molecular weights with apparent P s that can reach up to 10 repeat units (GPC). The use of dodecyl and ethylhexyl side chains is critical, because these enhance the solubility of the formed PPEs (4b and c). With hexyl side chains the degree of polymerization (P = 100) is not limited by the catalyst activity, but by the lack of solubility of 4a. 

FIGURE 39.3. Secondary nucleation plot for linear polyethylene (LPE) and ethylene-octene copolymers (isothermal data-filled symbols rapid cooling data-open symbols). For copolymers, L and H indicated low and high MW, respectively, and the number following the letters represents the number of hexyl side chains per 1,000 carbon atoms. Reproduced from [Polymer] (2001) [19] with permission from Elsevier. 

Figure 16 2D H- H DQ-SQ and C H FSLG-HETCOR NMR spectra of (A, B) PlOO and (C, D) P200, recorded at 20.0 T using spinning frequencies of 15.0 and 25.0 kHz, respectively. One rotor period of BaBa recoupling was used in (A, C), while a cross-polarization of 3.0 was used in (B, D). A, Cr, and HS refer to the amorphous, crystalline, and hexyl side chain, respectively. The asterisk in (D) marks an artifact from the carrier frequency. Copyright 2012 Wiley. Used with permission from Ref [194],...

Figure 17 (A) Packing model and (B) its corresponding NICS map for P3HTin bulksam-ples after annealing that bests fit with the experimental data. (C) Side and (D) top views of the same model shown without the hexyl side chains for clarity. The green (biack in the print version) arrows indicate thiophene H- H distances below 4 A, while the red (dark gray in the print version) arrows Indicate those that are above 4 A. Copyright 2012 Wiley. Used with permission from Ref. [194].

Scheme 4 10 Preparation of PPP with hexyl side chains." ...

Pd-catalyzed homopolymerization of 4,4 -diiodoazobenzene with hexyl side chains gives the homopolymer of azobenzene when bis(pinacolato)diboron is used as a condensation agent, as shown in Scheme 4.25. ... 

Fig. 2.1. Schematic illustration of polyethylene molecular structure of various density ranges (Elias 1992). Top LDPE, radical polymerisation yields a number of (long) side ehains. Bottom HDPE, catalytic polymerisation gives rise to linear ehains with a small number of short branches. Both drawings in the middle illustrate LLDPEs produced by catalytic polymerisation with a-olefines. Small amounts of bntene-1, hexene-1 or octene-1 co-monomers lead to etlyl, butyl or hexyl side chains. Polymerisation in the gaseous phase produces chains arranged in a block-shaped fashion and distributed at various frequencies along the chaia Solution phase polymerisation provides a statistical random distribution along the whole chain...

The adsorption of surfactant polymers onto hydrophobic substrates are found to be influenced by the hexyl side chains, while a protective antifouling layer is formed by the maltose dendron side chains inhibiting platelet adhesion. 

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