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 ...


12

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.


11

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 ...


7

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

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). ...


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

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

There is a misconception that runs through the questions, the answer key and the comments: For tripeptides, the peptide linkage is directional (i.e. the tripeptide has an amino terminal and a carboxy terminal), so ABC is different from CBA. To get the number of tripeptides combined from three types of amino acids, you have three choices for the first, ...


3

No, PET it is definitely not a copolymer. Neither is e.g. Nylon 6,11 (or any other polyamide with two numbers). The monomers alone would not polymerise, or at least only by a very different reaction (e.g. ethylene gylcol gives PEG). What you can have are alternating copolymers, but there the sequence is a statistical property. It comes when a reactive chain ...


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 ...


3

I think the meaning of the word "bulk" — as it is used in English language — is preserved here despite chemical context. I suspect that it's been used to stress some aspects or features of the surface chemistry: thin film is a 2D object, whereas bulk polymer is a 3D object (e.g. continuous in three directions) possessing a significant volume. From IUPAC's ...


3

According to Palstics International's Chemical Resistance Chart, the A-rated plastics (no solvent attack) towards acetone are: ECTFE (Halar®): transparent films available Fluorosint® PTFE: white HDPE: transparent films available Nylon®, Type 6/6: white PP: clear sheets available PPS: opaque white PTFE: white Among these, polypropylene appears to be the ...


3

Things are more complex than you suppose There are two key reasons why these compounds burn with different smells. The first is that your assumption about what the substances contain is wrong. Biological fibres contain plenty other than carbon and hydrogen. Often they will have lots of nitrogen and sulphur and various other elements and these often produce ...


2

I agree with the interpretation given by andselisk. The authors wish to differentiate thin films vs. bulk of the same polymeric material. One of meanings of bulk given in the unabridged Oxford English Dictionary [by subscription] is Magnitude in three dimensions; volume. 1825 J. R. McCulloch Princ. Polit. Econ. ii. ii. 141 They [gold and silver] ...


2

Plastics Design Library series include tabulated parameters for the variety of polymers. One of such parameters is a PDL number rating from 0 to 9: 0: solvent dissolved disintegrated 1: decomposition 2: severe distortion; oxidizer and plasticizer deteriorated … 9: highest resistance, no change In the table below I assembled data on thermoplastics ...


2

Fibres are made of long linear molecules, in which the atoms are bound by covalences C-C or C-O. Usually it is a long C-C-C-C-C-C-O-C-C-C, with one O from time to time. Such bonds are hard to break. But paralleled fibres are hold together by van der Wals forces, which are rather weak. They are not difficult to get separated. That is why a fiber can be ...


2

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. ...


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 ...


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

It should not be difficult to derive either of the number-averaged molecular weight or weight-averaged molecular weight by their definitions. To avoid ambiguity, I will use $i$ as the index of each actual length of chains and $b$ as the index of batches. First, the definitions: $\bar{M}_\mathrm{n,final}=\frac{\Sigma_in_iw_i}{\Sigma_in_i}$ $\bar{M}_\...


1

This a problem of radiation chemistry. It has been thoroughly studied in the years 1950 - 1960 - 1970 with gamma rays. When intense source of gamma rays strikes water, electrons are extracted from the water molecule. And some of these electrons are coming from the valence bond O-H. The bond is then weakened, and may even be broken. Usually the electron soon ...


1

The problems with reacting pure nylon salt are as follows: The molecules of hexamethylene diamine (HMD) and adipic acid will have a very hard time accessing each other's reacting groups, because of limited mobility within the solid structures. The reaction is a condensation, so it will produce a substantial amount of water anyway, so pretty much any reason ...


1

There is a slight deviation in the literature as to what the hybrid composites are. Originally, materials were considered hybrid composites if both inorganic (e.g. clay/silicates as the hydrophilic component) and organic (e.g. organic polymer as the hydrophobic component) constituents were involved in building up the matrix (see e.g. a review [1]). Another ...


1

Alternatively, cast your own sheet (or straight your close-to-final piece) using a mold from a chemical resistant 2 part epoxy. Usually, difunctional or polyfunctional amine hardeners confer chemical/temperature resistance, causing a polymerization in a 3D cross-linked network (it also means saying goodbye to thermoplasticity). Google search - customize it ...


1

I think the only real option for this is a clear plastic sheet that's had a chemical resistant thin film applied to the faces. One commercially available example is Makrolon AR2, it's polycarbonate with some proprietary coating that's listed as having >24hrs resistance to acetone and a few other chemicals.


1

Nylon 612, primarily used for filaments and toothbrushes, is resistant to clove oil at 20 °C [1, p. 2034]: Nylon 12, used for coatings, is also resistant to clove oil at 20 °C [1, p. 1829]: The tech data on nylon at newmantools.com also suggests there is no effect of clove oil on nylon in general. References Chemical Resistance of Thermoplastics; ...


1

What is happening is not actually the polystyrene melting but rather it dissolving in the acetone solvent. This is a physical change and not chemically altering the polymer. It should still retain its chemical properties as before. However, other properties have changed. It is now a poorer insulator since the air pockets have been removed. It will also be ...


1

I think your second quote is referring to some polymers such as sodium polyacrylate, $\ce{[-CH2-CH(COONa)$-$]_n}$. This polymer is basically just the sodium salt of polyacrylic acid (or polymerized sodium acrylate). You can see below the ionic bond between the anionic carboxylate group and the sodium cation: However, the quote could be referring to so-...


1

The given explanation cannot be correct, because I've watched (and listened to) an acrylic glass cracking and splitting and developing leaks after pouring in a splash of bourbon. No drying out is involved. It may be simply swelling of the plastic as ethanol penetrates; this could cause cracks if the bulk of the plastic is too rigid to stretch, and can't ...


Only top voted, non community-wiki answers of a minimum length are eligible