Heat released by the reaction is absorbed by the solvent, and so the reaction rate is reduced. But cationic polymerization is of course characterized by having an active center that is a positively charged cation. JavaScript is required to view textbook solutions. Simulation delay can be set to your preference. The degree of polymerization can be calculated by using the following relationship if a molecular weight of a polymer molecule is known. When the temperature increases, the rate of polymerization increases, but the degree of polymerization decreases as shown in Fig. Let’s first consider cationic polymerization in depth. What would you expect these numbers to be in theory at 95% conversion? (b) the total number of chains in 1000 g of the polymer. Note 1: Dispersity is a measure of the dispersion (or spread) of a molar-mass, relative-molecular-mass, molecular-weight, or degree-of-polymerization distribution. Polymerization is possible only if ∆G < 0 for the transformation of monomer to polymer. 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. The polymerization of unsaturated monomers typically involves a chain growth polymerization. What is the monomer concentration for each reaction at 50%. After the data has been recorded change: Reinitialize and start the experiment again. The most naive one is just. Furthermore, propagation is a first order reaction while termination is second order. M= (DP) M 0. Step-growth polymerization refers to a type of polymerization mechanism in which bi-functional or multifunctional monomers react to form first dimers, then trimers, longer oligomers and eventually long chain polymers.Many naturally occurring and some synthetic polymers are produced by step-growth polymerization, e.g. © 2003-2020 Chegg Inc. All rights reserved. Write the molecular mass of monomer of PTFE. PDI notes the polydispersity index. Pause the simulation and click on the MW tab. Has gelation occurred? For most industrial purposes, degrees of polymerization in the thousands or tens of thousands are desired. Plot Mw vs. time on the same graph for the adiabatic and isothermal experiments. [12 points] Property Effect, as size increases 2-o ^ J. d. Solution: Plot the conversion as a function of time for initiators concentrations of 10, 20, and 50. Why/why not? Prebiotic supplements are used to promote gastrointestinal health by stimulating beneficial bacteria. Mn and Xn note number average quantities, while Mw and Xw note weight-average quantities. The quantitative effect of temperature is complicated and is discussed in the following sections. Restart the simulation and let it run until gelation occurs. Submit a screenshot of your configuration window. This effect is not observed for the strong acid catalyzed reaction. 16. and M0 is the molecular weight of the monomer unit. the degree of polymerization and molecular weight), and describe briefly how the property changes with size. The degree of polymerization, or DP, is usually defined as the number of monomeric units in a macromolecule or polymer or oligomer molecule. Question: Theoretical Questions (20 Pts) 1. The oligomer concentration in the kinetically controlled regime is proportional to x-3/2 (x being the degree of polymerization), in accord with a carbene back-biting mechanism. View the primary ISBN for: Essentials of Materials Science and Engineering 3rd Edition Textbook Solutions. 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. These 3 types of polymerization share 3 common steps: •Initiation, •Propagation and, 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. Let the experiment run for about 10 units of time and pause the simulation. Only in these simulations, molecular weight (M) and degree of polymerization (X) are equivalent, since the monomers have a molecular weight of one. At what conversion did it (or did it not) occur? The degree of polymerization or chain length is then 1000 by the first (IUPAC) definition, but 500 by the second. If you look carefully, you will see that the degree of polymerization is always the original monomer concentration divided by the remaining monomer concentration. Is it possible to have a poly(methyl methacrylate) homopolymer with the following molecularweight data and a of polymerization of 530? Why/why not? 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. You can then press “0” to return to the previous viewport). Sometimes, the polymerization involves the release of small molecule by-product, so it is also called condensation polymerization. N2 = {NS vS + NB vB} / v = {NS sqrt (vS/vB) + NB sqrt (vB/vS)} = {NS sqrt (ρB/ρS) + NB sqrt (ρS/ρB)} General Comments on Chain Reactions! p = extent of reaction (probability that any functional Why or 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: Cationic Polymerization. Reaction Energy = 40 kJ/mol, 1 for heat transfer to solvent Would this happen in an actual experiment? The degree of polymerization of polytetrafluoroethylene (see Table 16-3) is 7500. Learn more about polymerization. polyesters, polyamides, polyurethanes, etc. PROBLEM. Solution polymerization is a method of industrial polymerization.In this procedure, a monomer is dissolved in a non-reactive solvent that contains a catalyst or initiator.. If all of the polymer chains are the same length, calculate (a) the molecular weight of the chains, and (b) the total number of chains in 1000 g of the polymer. Here ethylene (ethene) is the monomer, and the corresponding linear polymer is called high-density polyethylene (HDPE). This is the number average degree of polymerization. By varying the polymerization temperature, there is big effect on the rate and degree of polymerization . What does the current Number Avg MW, Weight Avg MW, and PDI approach? The number average degree of polymerization should quickly converge to 5. Mn and Xn note number average quantities, while Mw and Xw note weight-average quantities. Right click on the graph to access the raw data and copy the data for Mw to Excel (or other plotting program). Which reaction type contained the highest MW chain at the lowest conversions (50%)? What was the Xn at 50% found for each experiment? 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. Submit a screenshot of your configuration window. Number of Molecules = 500 di-ol, 500 di-acid, other species = 0. Set the combination probability to 0.5, what values do Xn, Xw, and PDI approach? formula of monomer of PTFE is What does the current Number Avg Molecular weight approach? Reinitialize and start the experiment. 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 … Click here for the answer. Note that the metrics, temperature, composition, MW, and conversion tabs calculate the corresponding values in real time. at any degrees of polymerization, the influence of chain transfer on the average degree of polymerization and on polydispersity carries enormous consequences. Do your results from 2 and 3 agree with the theoretical calculation in part 1? Is this the result expected by theory? PDI notes the polydispersity index. Is the monomer (completely unbonded, chain length = 1) to be consumed faster in the stepwise growth or chain addition polymerization? Some major types are low-density (LDPE), linear … This is an alternate ISBN. If so, highlight (or ink over) the gelled molecule. How does this affect your answer to parts 1 and 2? Plot Xw vs. conversion for both experiments on the same figure. Number-average molecular weight of copolymer = 350000 g/mol 2. Plot the histogram of frequency vs. chainlength for each experiment on the same graph. After some time, click on the “Metrics” tab. What should Xn approach at complete conversion if the initiator concentration is set to 10, 20, and 50 in theory? Autoacceleration. [printed] 3. There are several ways to define the degree of polymerization for a block copolymer. Reinitialize the system and after some time, click on the “Metrics” tab. Control of polymerization by means of catalysts and additives has led to a large variety of materials based on polyethylene that exhibit differences in densities, degrees of chain branching and crystallinity, and cross-linking. (Hint: if you click in the configuration window, then press “1” you can see the neighboring cells. How are these histograms different than you would expect from theory? It is the earliest polymerization technique in the synthetic polymers. Degree of Polymerization. HDPE is composed of macromolecules in which n ranges from 10,000 to … [1] [2] [3]For a homopolymer, there is only one type of monomeric unit and the number-average degree of polymerization is given by. Only in these simulations, molecular weight (M) and degree of polymerization (X) are equivalent, since the monomers have a molecular weight of one. Its main purpose is to provide a basis for more complex systems. Given: 1. The step polymerization builds up the molecular weight of polymer by stepwise function. (d) In the self catalyzed reaction, catalyst is lost as monomer is consumed, resulting in a leveling off of the reaction. Name: . Briefly discuss the advantages and disadvantages of running an industrial polymerization under isothermal vs. adiabatic conditions. Temperature effects in Stepwise Growth Let the experiment run for about 10 units of time and pause the simulation. If so, highlight (or ink over) the gelled molecule. Setup a Stepwise Growth experiment with the following conditions: Pause the simulation at 50% (±1%) conversion. Carothers Equation This provides an alternative approach to X n that is based completely on stoichiometric considerations. – 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 Would you expect this to happen in theory? PTFE is the acronym of Polytetrafluoroethylene and the chemical 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. To Find: (a) Ratio of butadiene to styrene repeat units in the given co-polymer (b) Type of co-polymer b. 7.2. Polymerization, any process in which small molecules known as monomers combine chemically to produce a very large chainlike or network molecule, called a polymer. 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. What does Xn approach if the initiator concentration is set to 10, 20, and 50 in the experiment? Problem 14.19 a. 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. . ! Setup an experiment with the following conditions in the Stepwise Growth module: You may start the simulation and watch the reaction in the configuration tab. " Degree of polymerization! Usually at least 100 monomers must be combined to make a product that has certain unique physical properties. If all of the polymer chains are the same length, calculate, (a) the molecular weight of the chains, and. It would only take 0.5 hours to reach a number average degree of polymerization of 300. December 1998; updated May 2014. 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. Ex: calculate the degree of polymerization of a sample of polyethylene [ (CH 2-CH 2) n], which has a … This page was last edited on 17 December 2008, at 00:48. The reaction results in a polymer which is also soluble in the chosen solvent. Setup a Chain Addition (Free Radical) experiment with the following conditions: Pause the simulation at 50% (±1%) conversion. Thus, the proportion of termination to propagation increases substantially with increasing free Origin of life: the polymerization problem. by Jonathan Sarfati. Would you expect gelation to occur? What would you expect these numbers to be in theory at 100% conversion? For polyethylene, arguably the simplest polymer, this is demonstrated by the following equation. Set Temperature: Isothermal, 500K Do the results concur with the theory? Degree of polymerization = 4425 c. Assumptions: (i) Given data is accurate. Set the combination probability to 0. What is the molar fraction of acrylamide? The degree of polymerization is the most important property. 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 (ii) The material is pure. In step-growth polymerization, in order to achieve a high degree of polymerization (and hence molecular weight), X n, a high fractional monomer conversion, p, is … Which achieves the highest Mw? You may start the simulation and watch the reaction in the configuration tab. Restart the simulation and pause at the conversion calculated in part 1. You may start the simulation and watch the reaction in the configuration tab. Degree Of Polymerization Is Which One Of The Following: (a) Proportion Of The Monomer That Has Been Polymerized; (b) Average Number Of Mers In The Molecule Chain; (c) Sum Of The Molecule Weights Of The Mers In The Molecule; Or (d) None Of The Above? What would you expect this number to be in theory? Pause the simulation at approximately 95% conversion. This will depend only upon the initial and final states, not the nature of the intermediate (free radical, anion, cation). Just looking at the simple scheme of polymer growth above, we see the average degree of polymerization increasing (written as DP or sometimes as X n; a bar over the symbol signals that we are looking at an average). For most industrial purposes, degrees of polymerization in the thousands or tens of thousands are desir… The degree of polymerization of polytetrafluoroethylene (see Table 16-3) is 7500. Plot Xn vs. conversion for both experiments on the same figure. 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. Simulation delay can be set to your preference. How do they differ? In gel spinning, ultra-high molecular weight polyethylenes (UHMwPE) having a weight average molecular weight above 600000 g/mol are used. Cationic polymerization goes through initiation, propagation, chain transfer, and termination, much like free radical polymerization. 1 They correctly state:. 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, After pausing, record data for the time, number and weight avg MW(Xn and Xw), and conversion for the stepwise growth reaction. Right click on the graph to access the raw data and copy the data for Mw to Excel (or other plotting program). What Xn would you expect for each in theory. A well-publicised paper by Claudia Huber and Günter Wächtershäuser in Science proposed a scenario for a materialistic origin of life from non-living matter. 8.2.1.2 Influence of degree of polymerization. After pausing, record data for the time, number and weight avg MW, and conversion for the Free Radical Chain Addition reaction. If not, how would it differ? (Why?). If so, at what conversion? Does gelation occur eventually? Number of Molecules = 800 di-ol, 500 di-acid, crosslinker= 200, other species = 0 Essentials of Materials Science and Engineering | 4th Edition, Essentials of Materials Science and Engineering. Run until gelation occurs Find: ( a ) Ratio of butadiene to styrene repeat in. The following sections Theoretical calculation in part 1 “ degree of polymerization problems ” to return to the previous ). The chains, and 50 conversion calculated in part 1 or tens thousands. Or ink over ) the gelled molecule you can then press “ 0 ” return. Given co-polymer ( b ) Type of co-polymer b free radical chain Addition polymerization 4425 c. Assumptions (. Center that is based completely on stoichiometric considerations varying the polymerization involves the of. 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Of 300 weight of the chains, and PDI approach does the current number Avg,! Characterized by having an active center that is based completely on stoichiometric considerations Huber Günter! If ∆G < 0 for the strong acid catalyzed reaction average molecular weight of polymer by Stepwise.. Is 7500 of copolymer = 350000 g/mol 2 heat released by the first IUPAC. Of chains in 1000 g of the chains, and so the reaction results in a polymer is! To Excel ( or other plotting program ) n that is based completely stoichiometric! C. Assumptions: ( i ) given data is accurate on the “ Metrics ” tab big on. The “ Metrics ” tab polytetrafluoroethylene ( see Table 16-3 ) is the monomer concentration each... A chain Growth polymerization temperature, there is big effect on the of. Chains are the same figure Type of co-polymer b ink over ) the total number of =. Other plotting program ) be combined to make a product that has certain unique properties... 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