Degradation low molecular weight

Vander Jagt, D. L., Hunsaker, L. A., and Campos, N. M. (1986). Characterization of a hemoglobin-degrading, low molecular weight protease from Plasmodium falciparum. Mol. Biochem. Parasitol. 18, 389-400. 

Dozens of environmental microbes have been reported to degrade PLLA or PDLLA [189]. The PLLA and PDLLA in the environment are assumed to initially undergo chemical hydrolytic degradation followed by the bioassimilation of degraded low molecular weight lactic acid oligomers and monomers [288]. The mineralization of PLLA by microbes to form CO2 occurs in soils [289] and compost [290]. The microbes in compost induce degradation... 

The 7-modification of iPP (y-iPP) may form in degraded, low molecular weight iPP or in samples crystallized under high pressure [5, 6]. Certain propylene copolymers with low comonomer content (4-10 wt.%) crystallize preferentially in y-form, as well. y-iPP has a face-centred ortho-rombic unit cell with parameters a = 0.85 run, b = 0.993 nm and c = 4.241 nm containing isochiral helices. The cell structure proposed by Bruckner et al. [5] is unique in polymer crystallography the chain axes in adjacent crystal layers are not parallel. The angle between the chain stems is about 80°. y-iPP is not usually observed as an independent phase, but crystallizes with and within the a-spherulites. According to Lotz et al. [7], the positive spherulites observed in samples with mixed polymorphic composition of a- and y-iPP are probably made of a... 

The thermal degradation of mixtures of the common automotive plastics polypropylene, ABS, PVC, and polyurethane can produce low molecular weight chemicals (57). Composition of the blend affected reaction rates. Sequential thermolysis and gasification of commingled plastics found in other waste streams to produce a syngas containing primarily carbon monoxide and hydrogen has been reported (58). 

A number of physical and chemical properties of 1-propanol are Hsted ia Table 1 (2,3). The chemistry of 1-propanol is typical of low molecular weight primary alcohols (see Alcohols, higher aliphatic). Biologically, 1-propanol is easily degraded by activated sludge and is the easiest alcohol to degrade (4). 

It is now generally used ia the form of a Hquid, low molecular-weight polymer, having reactive end groups obtained by degradation of the base polymer, as foUows ... 

There is much evidence that weak links are present in the chains of most polymer species. These weak points may be at a terminal position and arise from the specific mechanism of chain termination or may be non-terminal and arise from a momentary aberration in the modus operandi of the polymerisation reaction. Because of these weak points it is found that polyethylene, polytetrafluoroethylene and poly(vinyl chloride), to take just three well-known examples, have a much lower resistance to thermal degradation than low molecular weight analogues. For similar reasons polyacrylonitrile and natural rubber may degrade whilst being dissolved in suitable solvents. 

PVC has a rather limited thermal stability. This is rather surprising since it is known that low molecular weight materials containing similar structures cire far more stable. It would thus appear that this instability is due to imperfections or weak points in the structure at which degradation can commence. The... 

The author is unaware of any commerical polymers that are specifically designed to degrade oxidatively, although oxidation may be involved in association with hydrolytic and biological degradation. It may be of interest to note that before World War II products known as rubbones were produced by degrading natural rubber with cobalt linoleate in the presence of cellulosic materials to produce low molecular weight, fluid oxidised natural rubber (Section 30.4). 

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