17

The scientist who coined the term polymer, Jöns Jacob Berzelius, used the word to refer to different substances which had the same empirical formula. In this sense, benzene is a polymer of ethyne (acetylene), because benzene $\ce{C6H6}$ and ethyne $\ce{C2H2}$ have the same empirical formula, namely $\ce{CH}$. In other words, all substances with molecular ...


14

I use ChemDraw Professional 19.1.1.32. If you follow File>Open Templates>Advanced BioDraw, you will find the black helix that I have reoriented from horizontal to vertical. The red helix was enlarged and colored red. I hope this is of help.


12

This illustration may be a combination of two images, or simply a program I don't know about. However, there are many (3D) protein visualisation programs that can show alpha-helices such as PyMol, VMD or Yasara. Here you can ray-trace the image (i.e. transparent background) and then combine the illustration with something else, e.g. an illustration from ...


9

I was able to reach the manufacturer and ask her directly. USPXX is the "edition" of the US Pharmacopeia's "exams" that a product must pass in order to be considered pharmaceutical grade. As time goes on, these exams may get updated and improved. So a higher number USPXX means that a product passed a more recent (and likely, more ...


8

This answer is for ChemDoodle, but I think you can import SVG files into ChemDraw as well. Just take an SVG image of an alpha helix and copy and paste it into ChemDoodle. Or go to File -> Insert Image and select the SVG file from your computer. It doesn't have to be SVG, but they have advantages with scaling. Made this using this File from Wikipedia, but ...


6

Normally, in practice the amount fraction of DVB in the feed is used as a nominal number for the degree of crosslinking. IUPAC provides a definition in a somewhat unexpected place [1, p. 2352]: Crosslinking: Property of a solid support prepared from polymeric materials with interconnected strands. Often results from the inclusion of multifunctional monomers ...


6

Short answer: Yes and No, depending if we consider polymer(1) or polymer(2). Long answer: The first step in decision "Is X A or not ?" must be clarification what we mean by "A". Benzene is a cyclic trimer of ethyne. Trimers are a special case of polymers(1) as repeated monomer structures, being a superset of oligomers and polymers(2). ...


5

The value $\bf{4-88}$ can be described as follows: $\bf{4}$: This represents the viscosity (in $\pu{mPa s}$) of a $4\%$ solution in water at $\pu{20 ^\circ C}$. This value is somewhat proportional to the molecular weight of the polymer chain. $\bf{88}$: This represents the percentage of moles of acetate ester that were hydrolyzed, since polyvinyl alcohol is ...


4

Not really. As long as you are in solution (=unreacted monomer or solvent), it makes no difference if the reactive chain end is diffusing slow or fast. The monomer molecules come by at the same rate. The mobile chain end would help against a local depletion of monomer, but once your mixture gets so viscous that this could happen, neither a long or a short ...


4

It certainly would be possible to get an indication of some of the sources of carbon through mass spectrometry and through radiocarbon dating. For example, fossil carbon sources would have little 14C, sources predating the 20th century, e.g. older trees, would have more. Post-Atomic Age sources might have more yet, beyond that due to natural decay of 14C. ...


4

PETG is also not resistant against toluene. A month-long contact under ambient conditions results a complete swollen/disintegrated PETG material (PDL rating 0), and an year-long exposure even causes whitening [1, p. 2660]: References Chemical Resistance of Thermoplastics; Woishnis, W. A., Ebnesajjad, S., Eds.; PDL handbook series; William Andrew: ...


4

The property of "moldability" can be based on several properties of plastics There are broadly two types of polymer commonly used. Polymers that set and thermoplastics that can be molded when hot. Both of these types can have the desirable property of being liquids that can fill a complex mold before becoming rigid (though by far the commonest is ...


3

First lets take a look at o-pthalic acid and it's anhydride. Now as you can see the ring formed in case of o-pthalic anhydride is sterically feasible. There is not very high angle strain and the aromaticity is still intact. Now, take a look at p-pthalic acid. Now, if you try to dehydrate this molecule as you see there is a very big steric problem. To ...


3

Note that branching is not unheard of, for instance glutathione is an abundant short branched peptide formed by condensation of the carboxylic group on a glutamic acid side chain to the main chain amino group of a cysteine aminoacid. This requires a dedicated enzyme both for synthesis (glutamate cysteine ligase) and degradation of the gamma peptide bond. ...


3

According to NASA1 the main factor inhibiting the widespread use of polymer materials in space environments is oxygen erosion, the materials tested so far to be proven effective in space are Teflon, Mylar, Kapton and Tedlar. Further experimentation is being conducted on board ISS according to their website2. I do not believe there are polymers currently ...


2

Polymerizations expelling water, equally known as polycondensation (PET is a typical product), are a subset of polymerizations. The radical polymerization here is more likely to proceed differently with three reaction types running concurrently: initiation, propagation, and termination. During the initiation, light splits the phenylketone into two fragments ...


2

An image of the CPVC effect is shown in the diagram below. The red color is the binder, the black is the pigment and the white is air (because there is not enough binder to coat all the pigment). The lines depict the change in properties you would expect, and you already have the formula to correlate the paint properties with the raw material properties. ...


2

Propene performs radical ( denoted by $\cdot$ ) driven polymerization: $$\ce{R. + CH2=CH(CH3) -> R-CH2-CH(CH3).}$$ where the radical end is eventually terminated by recombination,stopping the polymerization. Polymerizations typically convert a double bond of a monomer to a single bond, freeing extra electrons to create extra bonds between monomers. OTOH, ...


2

Proteins are built from monomers with only two linking groups The monomers that make up proteins join in very specific ways. The general structure is: where R can be a variety of possible groups. To form a protein the monomers join when the amino group reacts with the carboxylic acid group. this gives a product with a specific orientation and which still ...


2

The broad question here is whether "non-recyclable" plastics can be turned into fuel. The short answer to that is yes. More on that below. However, the specific proposal to convert polystyrene to isooctane is not particularly feasible. I'll address that first. The proposed process begins with depolymerization of polystyrene back to styrene. ...


1

This is really a plumbing issue much more than a chemical dissolution issue. The problem is uncertain: "seems" to be a latex rubber glove; complete blockage. I'm trying to envision how a rubber glove completely blocks a drain. Perhaps by partially blocking the drain, then catching hair and other particles - but on what? Perhaps on something else ...


1

I think the authors' choice of words might have confused you a bit. We found that neither the ultrafine Teflon particles alone when generated in argon nor the Teflon fume gas-phase constituents when generated in air were toxic after 25 minutes of exposure. What the authors mean is that when they used only ultrafine Teflon particles on the rats it did not ...


1

I contacted GoodFellow directly and they gave me the following answer: 93.9% AN: 93.9% AcryloNitrile 5.8% MA: 5.8% Methyl Acrylate 0.3% MS: 0.3% Methyl Sulfonate I guess different manufacturers may name their products as they see fit. In particular, for polymers that can share the same abbreviations, only the context and a good background knowledge of ...


1

The term «polymer» only refers to using small molecules (called «monomer», needn't be of one type) multiple times to build a larger molecule. E.g., if you would use the small molecule thrice to get a larger one, it were a trimer, if four times, a tetramer to be more specific; but these were all examples of «polymers». The term does not tell if the material ...


1

There is this research on Chinese equivalent of seasoning process called "Kitchen God's Blessing" [1]. They argue that the non-stick property of seasoning comes by iron oxide $(\ce{Fe3O4})$ nanoballs. If they are correct then the oil or its polymers is not exactly what is causing the non-stick property but the those nanoballs on the surface. Their ...


1

A useful criterion I learned in organic chemistry: It is a polymer if removal of one or so monomers from the end does not change the properties, like viscosity significantly. You can use this rule of thumb to distinguish between oligomers and polymers in general. So by this account, benzene is definitely not a polymer.


1

“Branched chain” simply means that the main carbon backbone has other, smaller carbon backbones coming off of it. You’re correct, a hydrogen atom would have to be removed from a carbon atom in order to attach another polymer chain. Generally, branched chains decrease the density of a polymer because they fill space less efficiently than a perfectly straight ...


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