degree of polymerization problems

December 25, 2020 - Less than a minute read

p = extent of reaction (probability that any functional Plot the histogram of frequency vs. chainlength for each experiment on the same graph. Would you expect this to happen in theory? What does Xn approach if the initiator concentration is set to 10, 20, and 50 in the experiment? What was the Xn at 50% found for each experiment? Furthermore, propagation is a first order reaction while termination is second order. Setup a Stepwise Growth experiment with the following conditions: Pause the simulation at 50% (±1%) conversion. The degree of polymerization can be calculated by using the following relationship if a molecular weight of a polymer molecule is known. It would only take 0.5 hours to reach a number average degree of polymerization of 300. But cationic polymerization is of course characterized by having an active center that is a positively charged cation. " Degree of polymerization! 8.2.1.2 Influence of degree of polymerization. Why/why not? (Why?). Note that the metrics, temperature, composition, MW, and conversion tabs calculate the corresponding values in real time. Which reaction type contained the highest MW chain at the lowest conversions (50%)? The degree of polymerization, or DP, is usually defined as the number of monomeric units in a macromolecule or polymer or oligomer molecule. The repeating structural unit of most simple polymers not only reflects the monomer(s) from which the polymers are constructed, but also provides a concise means for drawing structures to represent these macromolecules. Do the results concur with the theory? If not, how would it differ? At what conversion did it (or did it not) occur? What should Xn approach at complete conversion if the initiator concentration is set to 10, 20, and 50 in theory? After some time, click on the “Metrics” tab. There are several ways to define the degree of polymerization for a block copolymer. You may start the simulation and watch the reaction in the configuration tab. Cationic polymerization goes through initiation, propagation, chain transfer, and termination, much like free radical polymerization. This effect is not observed for the strong acid catalyzed reaction. Click here for the answer. PDI notes the polydispersity index. What would you expect these numbers to be in theory at 95% conversion? It should be noted that the degree of polymerization refers to the number of monomers in the chain, but the degree of polymerization and molecular weight are used interchangeably in this simulation since each of the monomers is assumed to have a molecular weight of 1. – overall degree of polymerization: – block sequence: – statistical segment lengths: χ AB, χ BC , χ AC f A, f B, f C ( fc =1− fA − fB) N b A,b B,b C ABC, BAC, ACB Universal organization of phase behavior for ABC triblocks not yet known ABC Phase Behavior for ABC Triblock Copolymers 7.2. polyesters, polyamides, polyurethanes, etc. (Hint: if you click in the configuration window, then press “1” you can see the neighboring cells. (b) the total number of chains in 1000 g of the polymer. Number of Molecules = 200 di-ol, 200 di-acid, other species = 0, Number of Molecules = 10 initiator, 400 monomer, Initiator Reaction Energy = 0 kJ/mol, Radical Reaction Energy = 0 kJ/mol. Setup a Chain Addition (Free Radical) experiment with the following conditions: Pause the simulation at 50% (±1%) conversion. Why/why not? The number average degree of polymerization is given by (1) DP = X n = M n M 0 where Mn is the number average molecular weight and M0 is the molecular weight of the monomer In step growth polymerization, Xn can be related to the fractional monomer conversion as follows: If so, highlight (or ink over) the gelled molecule. Degree of polymerization = 4425 c. Assumptions: (i) Given data is accurate. Submit a screenshot of your configuration window. M is the molecular weight of the polymer, DP is the degree of polymerization and the M 0 is the formula weight of the repeating unit. Does gelation occur eventually? Reaction Energy = 40 kJ/mol, 1 for heat transfer to solvent If so, highlight (or ink over) the gelled molecule. Set the combination probability to 0.5, what values do Xn, Xw, and PDI approach? The most naive one is just. Restart the simulation and pause at the conversion calculated in part 1. The reason why such high molecular weight is necessary is believed to be as follows: supposing the perfect orientation of all molecular chains, the chain ends still remain as defects and these defects … Pause the simulation at approximately 95% conversion. [printed] 3. ! Last edited by Wchirdon 00:47, 17 December 2008 (UTC), Stepwise Growth vs. Chain Addition Polymerization, Free Radical Chain Addition Polymerization, http://rheneas.eng.buffalo.edu/w/index.php?title=Polymerization:Problems&oldid=2669, Number of Molecules = 250 di-ol, 250 di-acid, other species = 0, Simulation delay can be set to your preference. You may wish to slow the simulation by using the Simulation Delay tab on the left, and you may reinitialize the simulation if you overshoot. PDI notes the polydispersity index. For the CD shown on the table at the front of the room: a) Draw the polymer structure (we also discussed this polymer being used in drinking cups, [1] [2] [3]For a homopolymer, there is only one type of monomeric unit and the number-average degree of polymerization is given by. Why or why not? Is it possible to have a poly(methyl methacrylate) homopolymer with the following molecularweight data and a of polymerization of 530? Only in these simulations, molecular weight (M) and degree of polymerization (X) are equivalent, since the monomers have a molecular weight of one. For polyethylene, arguably the simplest polymer, this is demonstrated by the following equation. Here ethylene (ethene) is the monomer, and the corresponding linear polymer is called high-density polyethylene (HDPE). Set Temperature: Isothermal, 500K M= (DP) M 0. Plot Xn vs. conversion for both experiments on the same figure. Simulation delay can be set to your preference. Chain-growth polymerizations require the presence of an initiating molecule that can be used to attach a monomer molecule at the beginning of the polymerization. This is the number average degree of polymerization. Thus, the proportion of termination to propagation increases substantially with increasing free (d) In the self catalyzed reaction, catalyst is lost as monomer is consumed, resulting in a leveling off of the reaction. What would you expect these numbers to be in theory at 100% conversion? Learn more about polymerization. By varying the polymerization temperature, there is big effect on the rate and degree of polymerization . Other articles where Solution polymerization is discussed: chemistry of industrial polymers: Solution polymerization: The conducting of polymerization reactions in a solvent is an effective way to disperse heat; in addition, solutions are much easier to stir than bulk polymerizations. For most industrial purposes, degrees of polymerization in the thousands or tens of thousands are desir… Write the molecular mass of monomer of PTFE. Heat released by the reaction is absorbed by the solvent, and so the reaction rate is reduced. . Do your results from 2 and 3 agree with the theoretical calculation in part 1? Simulation delay can be set to your preference. Plot Xw vs. conversion for both experiments on the same figure. The quantitative effect of temperature is complicated and is discussed in the following sections. Mn and Xn note number average quantities, while Mw and Xw note weight-average quantities. After pausing, record data for the time, number and weight avg MW(Xn and Xw), and conversion for the stepwise growth reaction. A statistical copolymer formed from addition polymerization of acrylamide (71 g/mol) and methyl methacrylate (100 g/mol) has a molar mass of 11,955 g/mol with degree of polymerization of 150. Is the monomer (completely unbonded, chain length = 1) to be consumed faster in the stepwise growth or chain addition polymerization? Step Growth Polymerization 2 functional groups: a,b → form new link c, may be a side product d a—a + b—b → a—c—b +d For example, if a—a is a diacid and b—b is a diol: from diacid from diol Degree of polymerization ≡ number of monomer units or structural units incorporated in polymer chain = pn 2 n u n p M M ⋅ = where M Cationic Polymerization. Let the experiment run for about 10 units of time and pause the simulation. To Find: (a) Ratio of butadiene to styrene repeat units in the given co-polymer (b) Type of co-polymer b. Only in these simulations, molecular weight (M) and degree of polymerization (X) are equivalent, since the monomers have a molecular weight of one. Ethene ) is 7500 how are these histograms different than you would expect theory! Up the molecular weight approach a Stepwise Growth the degree of polymerization a. 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