Relationship between Particle Size and Molecular Weight of Rubber from Hevea Brasiliensis

Abstract

Rubber particles with different mean diameters obtained from fresh natural rubber latex (FL-latex) were separated by high-speed centrifugation. The small rubber particles (SRP), having mean diameter less than 250 nm, were found to be composed of both low and high number-average molecular-weight (Mn) rubber molecules; while larger rubber particles (LRP), with mean diameter larger than 250 nm, mainly consisted of low Mn rubber molecules. The content of longchain fatty acid ester are mainly due to functional groups such as phospholipids were less in SRP than that of LRP. This indicates clearly that LRP contains mainly rubber molecules which were terminated to form a functional terminal group containing fatty acid ester groups. The high molecular-weight rubber in SRP, containing lower amounts of ester groups, is presumed to be mainly linear molecules having no chain-end group to form branch-points. On the other hand, the low molecular-weight rubber molecules with high ester content in the LRP are presumably terminated with the functional group containing fatty acid esters to form long-chain branching. The molecular-weight of rubber in LRP increased with increasing particle sizes. This suggests that the LRP was derived from the aggregation and/or association of functional groups at ω- and α-terminal end groups.

Histochemical study of detailed laticifer structure and rubber biosynthesis-related protein localization in Hevea brasiliensis using spectral confocal laser scanning microscopy

“…Furthermore, it has been suggested that LRP was derived from the aggregation and/or association of functional groups at both terminal end groups of rubber molecules (Tarachiwin et al 2005). Together, our results that LRP localized in all laticifer layers including those where laticifer structures were disintegrated and rays were not functioning suggest that the role of REF might relate to termination of rubber elongation.…”

“…In H. brasiliensis, they have bimodal size distribution in fresh latex. Large rubber particles (LRPs) and small rubber particles (SRPs) show diVerences not only in molecular weight distribution and molecular structure but also in their surface proteins (Bahri and Hamzah 1996;Sakdapipanich et al 1999;Ohya et al 2000;Singh et al 2003;Tarachiwin et al 2005). Immunogold electron microscopy has shown that 14-and 24-kDa proteins are localized abundantly on LRPs and SRPs, respectively (Bahri and Hamzah 1996;Singh et al 2003).…”

Determination of configurational isomers in polybutadienes by 1H and 13C NMR spectroscopy

“…Practically all trans 1,4 and cis 1,4 polymers can be prepared from them via preparative techniques [100]. As for natural rub bers, the studies by Tanaka et al [101] showed that, in macromolecules of these natural polymers, the trans 1,4 configuration is represented by two to three units solely. At a molecular mass on the order of 10 5 , this implies that the case in point is the polymer containing 99.98% cis 1,4 configurations.…”

Protein‐based bioplastics and their antibacterial potential

“…15 For antibacterial analysis, various materials were purchased for testing: bacto tryptic soy agar and broth from Bectin, Dickinson and Company (Sparks, MD); Dey-Engley neutralizing broth from Remel (Thermo Scientific, Suwanee, GA); agar-agar solution that consisted of granulated agar-agar from EMD (Gibbstown, NJ); sodium chloride from Baker (Phillipsburg, NJ); and phosphate-buffered saline solution from HiMedia (Mumbai, India). Plasticizers were purchased through various sources: deionized water was supplied by a water filtering system in the lab; glycerol was obtained from Sigma-Aldrich with a purity 99%.…”