Influence f Plyether Cplymer Cnfiguratin n Plyurethane Reactin: A Mass Spectrmetry Analysis Influence f Plyether Cplymer Cnfiguratin n Plyurethane Reactin: A Mass Spectrmetry Analysis 1 Wu Suen, 1 Jennifer Percy, 1 Shaw L. Hsu *, 2 Igr A. Kaltashv and 2 Hward D. Stidham 1 Plymer Science and Engineering Department and Materials Research Science and Engineering Center 2 Chemistry Department, University f Massachusetts at Amherst, Amherst, Massachusetts 01003, USA Received: 1 August 2002 Accepted: 9 January 2003 ABSTRACT Matri Assisted Laser Desrptin Inizatin Time-f-Flight mass spectrmetry has been applied t btain the mlecular weight distributin f tw plyether cplymers cntaining ethylene ide and prpylene ide units. The measured mlecular weights and their distributins were surprisingly different frm the epected. Based upn the natural istpic abundance, it was pssible t prvide a quantitative descriptin f the number f ethylene ide and prpylene ide units as a functin f mlecular weight. Imprtant infrmatin n cmpsitin drift and hetergeneity can be btained frm the 3-D bivariate decnvlutin f the mass spectra. As the mlecular weight f a randm cplymer increased, the ethylene ide cntent als increased. A cplymer system with a narrw mlecular weight distributin did nt necessarily have a narrw cmpsitin distributin. These results prvide infrmatin at the mlecular level regarding the hydrphilicity f these cplymers used in plyurethane frmulatins. ITRDUCTI Intense research have revealed that the physical prperties f plyurethane fams directly depend n varius aspects f the phase separated mrphlgy (1-12). The urea and urethane segments frmed during the faming reactin typically aggregate and calesce int hard segment rich dmains. The fleible plyether cmpnents f the frmulatin frm the sft segments that cnnect the hard segment rich dmains, and this prvides the elastmeric prperties f plyurethane fams. Many factrs have been suggested that are capable f influencing the reactin kinetics, final mrphlgy and prperties f plyurethane fams. The influence f sft segments n the physical prperties T whm crrespndence shuld be addressed. Cellular Plymers, Vl. 22,. 1, 2003 23
Wu Suen, Jennifer Percy, Shaw L. Hsu, Igr A. Kaltashv and Hward D. Stidham f plyurethanes may be much mre significant than just being the elastmeric cnnecting elements f the dispersed hard segment dmains. The mlecular weight, functinality, and chemical cmpsitin may all play a significant rle in determining the develpment f mrphlgy and physical prperties. Tabr suggested that the miscibility f water with the reactant plyl may play a crucial rle (13). Recently in this labratry, cnsiderable attentin was paid t the miscibility behavir f the three principal cmpnents, plyether, water, and iscyanate. In a ne-sht prcess, these cmpnents must be physically mied in rder fr chemical reactin t ccur, as shwn schematically in Figure 1. When this is dne, urea hard segments first frm thrugh the plymerizatin f diiscyanates and water. This reactin is termed the blwing reactin because carbn diide is released as ne reactin prduct. The hydryl end grup f a sft segment then reacts with an iscyanate f a hard blck and creates a urethane linkage t frm the final plymer structure. As shwn in Figure 1, water must necessarily be in clse primity t the diiscyanates in the reactin scheme, and is cnsumed t frm hard segments with a distributin f lengths. The rigidity f the hard segments frmed and their length distributin are the primary driving frce that determines the final micrphase-separated mrphlgy. The hard segment length distributin CH 3 C C + H H C CH 3 H C H C CH 3 C C CH 3 H H + C 2 C CH 3 H CH 3 C C H C CH 3 H CH 3 C H C H-plyl-H plyl C H CH 3 CH 3 C H H H C plyl Figure 1 Reactin scheme f the plyurethane hard segment frmatin 24 Cellular Plymers, Vl. 22,. 1, 2003
Influence f Plyether Cplymer Cnfiguratin n Plyurethane Reactin: A Mass Spectrmetry Analysis plays an essential rle in determining the mechanical prperties f plyurethane fam (14). The dispersin f water when mied with plyl influences the hard segment distributin (15,16). Previus studies f the hard segment distributin in plyurethane fams indicated that increasing the water cntent f a fam did nt actually increase the mst prbable hard segment length, althugh it certainly increased the prprtin f the hard segment cmpnent. Rather, the amunt f water cntrlled the number f etra lng hard segments (15,16). By increasing the quantity f water, certain chains grw lnger at the epense f the majrity f the chains, and the additinal water des nt appear t be distributed equally amng the grwing hard segments. Cplymers f ethylene ide (E) and prpylene ide (P) are ften used as the plyether plyl system in plyurethane frmulatins. Ethylene ide is much mre hydrphilic than prpylene ide (1,13,17,18). The distributin f ethylene ide units in plyl mlecules is epected t be a crucial factr in determining the dispersin f water mlecules in the initial frmulatin. The miscibility f water in plyl is evidently determined in part by the cmpsitin distributin f the plyl. Since the miscibility f water in plyl is als strngly temperature dependent (13,18). The significant initial temperature jump (~130 degrees) that ccurs in the plymerizing bun shuld als significantly affect the kinetics, structure and mrphlgy f the final plyurethane fam (15,16). Different physical characterizatin techniques have been used t assess the miscibility behavir f water in plyls. Perhaps the mst cnclusive results were btained by using tubidimetric titratin (13). The micrphase frmatin in aqueus slutins f ne type f E/P blck cplymer was als analyzed with water cntent as variable (18). While these studies defined the phase behavir f different plyether plyls and water, a clear descriptin f hw the chemical structure f the plyl affects the miscibility behavir f water has yet t be accmplished. There have been a relatively small number f studies dealing with the sft segments. In mst cases, even the mlecular weight was nt determined definitively. Previus results f mass spectrmetry analysis indicated that fr lw mlecular weight plyl cplymers, it was pssible t analyze the ethylene ide and prpylene ide units by analyzing the mnistpic peak as lng as mass spectra with high enugh reslutin culd be btained (19). This prcedure becmes mre cmple as mlecular weight and cmpsitin hetergeneity increases. In this labratry, a number f techniques have been Cellular Plymers, Vl. 22,. 1, 2003 25
Wu Suen, Jennifer Percy, Shaw L. Hsu, Igr A. Kaltashv and Hward D. Stidham used t analyze plyether structure, including light scattering and vibratinal spectrscpy (20). In additin, matri-assisted-laser-desrptin-inizatin timef-flight mass spectrmetry (MALDI TF MS) has prved t be a pwerful technique in characterizing the mlecular weight distributin f hard segments in plyurethanes (15,16). In a number f ther studies, the end grup f synthetic plymers was characterized using these techniques (19,21-23). While mst f the reprted studies were cncentrated n hmplymers, relatively little wrk has been carried ut fr either randm r blck cplymers (19,24-29). This is due t the much mre cmple cmpsitin and mlecular weight distributin fr the cplymers, and t the limited reslutin achievable in the high m/z range f a typical TF mass analyzer. Hwever, even with these limitatins, in this wrk it has been pssible t deduce the mlecular distributin and chemical structure f tw plyls used in cmmercial fam frmulatins. Quantitative infrmatin was btained that measured the abundance f ethylene ide and prpylene ide units in each plymer chain as a functin f the methd f synthesis. These results are reprted belw. EPERIMETAL SECTI Materials Tw samples f plyether plyls were analyzed. Plyl A, prvided by Dw Chemical Cmpany, was a trifunctinal, randm cplymer f ethylene ide and prpylene ide plymerized with glycerin as initiatr. This plymer had secndary hydryl grups frm prpylene ide as end grups. The ethylene ide cntent was estimated at 13% (wt), crrespnding t a mlar rati f [E]/[P] = 1:5. Plyl B was a tri-blck cplymer with ethylene ide sequences capped by prpylene ide at bth ends (PP-PE-PP) (Aldrich, Milwaukee, WI). Its prduct infrmatin was available as MW n =3300 and 10% (wt) ethylene ide cntent. Mass Spectrmetry MALDI-TF measurements were perfrmed n a REFLE III (Bruker Daltnics, Billercia, MA) mass spectrmeter equipped with a 2 GHz digitizer. All eperiments were perfrmed in reflectin mde. Ins were generated by using a standard 337 nm nitrgen laser (pulse width f 3 ns). Each eperiment was preceded by eternal calibratin f the mass spectrmeter using a miture f peptides bmbesin, bradykinin, and bvine insulin (Sigma Chemical, St. Luis, M). 26 Cellular Plymers, Vl. 22,. 1, 2003
Influence f Plyether Cplymer Cnfiguratin n Plyurethane Reactin: A Mass Spectrmetry Analysis The plyl sample was disslved in THF (HPLC grade, Fisher Scientific, Pittsburgh, PA) at a cncentratin f 5 mg/ml, and mied with an equal vlume f saturated slutin f dithranl (Aldrich, Milwaukee. WI) which was used as a MALDI matri. All samples were prepared in 2 ml glass vials (VWR Scientific Prducts, Willard, H). After vigrus miing, 1 µl f the miture slutin was applied t the MALDI prbe. Each spectrum was accumulated by averaging at least 200 laser shts, and istpic reslutin f at least 4000 was achieved. Spectra were prcessed with Bruker tf 5.0.1 sftware, smthed with a 3 pint Sawitski-Glay filter, and the MW n, MW w and PDI was calculated fr each plymer sample. Each spectrum was cllected just abve the threshld f signal disappearance t avid in-surce fragmentatin and t maimize reslutin. RESULTS AD DISCUSSI The full mass spectrum f plyl A is shwn in Figure 2. The number average and weight average mlecular weights were calculated respectively as MW n a.i. 12000 10000 8000 6000 4000 3080 3090 3100 m/z 2000 1400 1900 2400 2900 3400 3900 4400 M/Z Figure 2 MALDI-TF mass spectrum f sample A, a randm cplymer f ethylene ide and prpylene ide with 13% ethylene ide by weight Cellular Plymers, Vl. 22,. 1, 2003 27
Wu Suen, Jennifer Percy, Shaw L. Hsu, Igr A. Kaltashv and Hward D. Stidham = 3085, MW w = 3102, giving a plydispersity inde (PDI) f 1.01. The inset shws the epanded regin arund the peak clusters with maimum signal intensity. The istpic reslutin achieved was crucial in further cmpsitin analysis f the plymer. The full mass spectrum fr plyl B is presented in Figure 3. The spectrum clearly indicates that this sample had 2 different mlecular weight fractins. A small amunt f a lw mlecular weight fractin was due t the presence f PP hmplymer (m/z < 1700). The majr cmpnent was a blck cplymer f PP-PE-PP (m/z > 2400). The mlar rati between these tw fractins was estimated at apprimately 1:5.5 as calculated by the rati f integrated areas, assuming n mass discriminatin tk place within the range f spectrum. The lwer mlecular weight hmplymer fractin is the plymerizatin prduct f etra amunt f prpylene ide, and independent f cplymerizatin reactin. Therefre, nly the cmpsitin f the dminant higher mlecular weight cplymer fractin was analyzed. The characteristics f this cmpnent are MW n = 3315, MW w = 3354, PDI = 1.01. The narrw mlecular weight distributin fr the cplymer fractin (plydispersity inde <1.05) validates the apprimatin a.i. 12000 10000 8000 6000 4000 3430 3440 3450 m/z 2000 500 1000 1500 2000 2500 3000 3500 4000 4500 M/Z Figure 3 MALDI-TF mass spectrum f sample B, a blck cplymer f ethyleneide and prpylene ide with 10% ethylene ide by weight 28 Cellular Plymers, Vl. 22,. 1, 2003
Influence f Plyether Cplymer Cnfiguratin n Plyurethane Reactin: A Mass Spectrmetry Analysis that the integrated intensity f the mass peak, calculated by integrating the peak area, was prprtinal t the mle fractin f the crrespnding mlecular ins (30). This is crucial fr the quantitative interpretatin f the mass spectrum. The features f the mass spectra that shuld be nted fr bth plyether cplymers were: 1) the spectra were cmpsed f mre than a hundred clusters f in peaks, spaced by 14 r 16 Da; 2) each cluster was cmpsed f several istpic peaks, with a spacing f 1 Da. These peaks were due t the istpic distributin in the plymer mlecules. The mnistpic mlecular weights fr the cmpnents ethylene ide (44.0261) and prpylene ide (58.0417), and the difference between them (14.1956), is small cmpared t the MW n (>3000). It is thus prbable that tw types f mlecules cntributed t ne cluster f peaks. In rder t assign the individual clusters and t determine the chemical cmpsitin f the sample, a rather labrius prcedure was necessary. Fr randm cplymer plyl A, each mlecule cntained a glycerin grup (MW 89.0237), 3 hydrgen atms (M H = 1.008) and segments f ethylene ide and prpylene ide. The ubiquitus sdium catin a + (MW= 22.9898) attached t the plymer mlecules prvided the single psitive charge. Therefre, the theretical mnistpic m/z values are (m/z) the = M glycerin + M a +3M H + n E M E + n P M P (1) = 115.0369 + n E M E + n P M P There are tw variables in this equatin, the number f ethylene ide and prpylene ide units. Therefre, additinal infrmatin is needed t determine the chemical cmpsitin f the sample. Earlier wrk suggested that the feed rati was such that ~13% ethylene ide was cntained in plyl A and ~10% prpylene ide in plyl B (14). This allwed a reasnable prcedure t be develped t determine the cmpsitin. Fr eample, cnsider the 3122.6 peak shwn in Figure 4a. A number f cmbinatins culd reasnably be assigned t this peak. Pssible mnistpic values clsest t 3122.6 were calculated as shwn in Table 1. T finalize the assignment amng these pssibilities, sme infrmatin regarding the apprimate plyl cmpsitin must be used. Based n the feed rati fr plyl A, the average mlar rati f ethylene ide t prpylene ide units shuld be apprimately 1:5. Thus, judging frm bth its small deviatin frm theretical mnistpic MW value and the rati 1:5 f n E /n P, a mlecule with n E =9 and n P = 45 (E9P45) was chsen as the mst prbable amng all the ther pssibilities. The mlecular frmula f E9P45 is then calculated t be C 156 H 314 57. Cellular Plymers, Vl. 22,. 1, 2003 29
Wu Suen, Jennifer Percy, Shaw L. Hsu, Igr A. Kaltashv and Hward D. Stidham Table 1 Pssible assignments f the mnistpic peak m/z 3122.6 in plyl A n e n p M W MW - MW calcul. calcul. e perim. 5 48 3121. 2 1. 4 9 45 3123. 1 0. 5 13 41 3125. 1 2. 5 30 29 3119. 0 3. 6 34 26 3121. 0 1. 6 38 23 3123. 0 0. 4 42 19 3124. 9 2. 3 59 7 3118. 8 3. 8 63 4 3120. 8 1. 8 Mre infrmatin n the cmpsitin can be btained by cnsidering the theretical istpe abundance pattern fr each mlecule (22,31,32). The cluster f m/z 3122.6 in the mass spectrum differed frm the theretical istpe pattern fr (E9P45+a + ) adduct in tw respects. First, the pattern f relative intensity f istpic peaks is cnsiderably different. Secnd, there are tw etra peaks with lwer m/z values in the cluster that are missing in the theretical istpe pattern. Further studies n these differences shwed that the tw etra peaks are part f the istpic peaks f a mlecule with 5 ethylene ide units and 48 prpylene ide units, designated E5P48, with mlecular frmula C 157 H 316 56. The pstulate that this cluster is cmpsed f 2 cmpnents, E9P45 and E5P48, eplains the appearance f the tw etra peaks, as shwn in Figure 4b. By carefully adjusting the relative rati f the 2 cmpnents t best match the measured istpe abundance, the mlar rati fr E9P45 t E5P48 was estimated as 2:1 as shwn in Figure 4c, with an errr <10%. The same analysis was applied t all remaining clusters f peaks in the mass spectrum. The fllwing rules were used t facilitate the assignment f the peaks: If a mlecular species with ethylene ide units and y prpylene ide units (E P y ) had m/z = n, then 30 Cellular Plymers, Vl. 22,. 1, 2003
Relative Istpe Abundance Influence f Plyether Cplymer Cnfiguratin n Plyurethane Reactin: A Mass Spectrmetry Analysis E9P45 E5P48 3115 3120 3125 3130 3135 M/Z 1.2 E9P45 (C 156 H 314 57 a) 1 0.8 E5P48 (C 157 H 316 56 a) 0.6 0.4 0.2 0 3115 3120 3125 3130 3135 M/Z Figure 4 a) Prpsed assignment fr the peak 3122.6 in plyl A; b) Theretical istpe distributin f mlecules E9P45 and E5P48; (cntinued) Cellular Plymers, Vl. 22,. 1, 2003 31
Wu Suen, Jennifer Percy, Shaw L. Hsu, Igr A. Kaltashv and Hward D. Stidham real peak 2*E9P45+E5P48 3115 3120 3125 3130 3135 M/Z Figure 4c) Cmparisn f the eperiment peak 3122.6 with the simulated peak: 2*E9P45 + E5P48 m/z mlecular frmula n+2 E +4 P y-3 n+14 E -1 P y+1 n+16 E +3 P y-2 n+44 E +1 P y n+58 E P y+1 Based upn the crrect assignment fr a few clusters, all ther clusters in the whle mass spectrum culd be assigned by applying these rules. There is still ne questin remaining, i.e., is it pssible that tw mlecules with different E/P cmpsitin can have m/z values s clse that they culd nt be differentiated by the mass spectrmeter? Simple calculatins suggest that the m/z value f the plymer (P) n-29 (E) m+29 is very clse t that f (P) n-7 (E) m. T see this, cmpare E 9 P 45 with E 38 P 22 in Table 1. The (P) n-29 (E) m+29 mlecule is t high in ethylene ide cntent, and is very unlikely t be present in the sample accrding t the feed rati making plyl A. With the crrect cmpsitin assignment made fr every cluster, and taking int accunt its peak intensity (prprtinal t mle fractin, see abve), we decnvluted 32 Cellular Plymers, Vl. 22,. 1, 2003
Influence f Plyether Cplymer Cnfiguratin n Plyurethane Reactin: A Mass Spectrmetry Analysis the spectra int a 3-dimentinal, bivariate functin (Figure 5). The vertical ais indicates the mle fractin f mlecules in the sample, while the hrizntal tw aes indicate the number f cnstituent ethylene ide and prpylene ide units. Based n these results, the calculated mlecular weight was MW n = 3047.5, which agrees within 1.2% with the eperimental value f 3085. As discussed abve that the mass spectrum f Plyl B shws tw fractins. These cnsist f a small amunt f lw mlecular weight ply(prpylene ide) hmplymer at m/z < 1700 (byprduct f cplymerizatin), and a large amunt f higher mlecular weight material due t the blck cplymer f PPG-PEG-PPG at m/z > 2400. By cnducting an analysis t the cplymer fractin in a way similar t plyl A, the 3-D, bivariate decnvlutin shwn in Figure 6 was btained. The number average mlecular weight was calculated as 3376.2, which agrees with the eperimental value 3315 within 1.8%. The distributin f hydrphilic ethylene ide and hydrphbic prpylene ide cmpnents in the plyl critically influences the miscibility and dispersin f water in the plyurethane frmulatin. It is f bth theretical and practical interest t analyze the cmpsitin distributin as a functin f mlecular 0.010 0.008 0.006 Relative Intensity 0.004 0.002 58 0 38 48 P units 5 10 E units 15 28 Figure 5 Three-dimensinal, bivariate decnvlutin f plyl A, with the Relative Intensity vs. the number f cmpnent E and P units Cellular Plymers, Vl. 22,. 1, 2003 33
Wu Suen, Jennifer Percy, Shaw L. Hsu, Igr A. Kaltashv and Hward D. Stidham 0.008 Relative Intensity 0.006 0.004 0.002 0 5 10 E units 45 15 35 65 55 P units Figure 6 Three-dimensinal, bivariate decnvlutin f plyl B, with the Relative Intensity vs. the number f cmpnent E and P units weight, and if pssible t determine the distributin f ethylene ide cntent. Further analysis f the 3-D bivariate functin prvides sme insight int the cmpsitin distributin. Figure 7 shws the relatin f ethylene ide cntent as a functin f mlecular weight in the randm plyl A t the ideal situatin when cmpsitin is independent f a change in mlecular weight. As the mlecular weight increases, the rati f the number f ethylene ide t prpylene ide units increases. This is in cntrast t the ideal assumptin that there is n cmpsitin drift as mlecular weight increases. This bservatin is als true fr blck plyl B, as shwn in Figure 8. These results clearly indicate a cmpsitin drift with mlecular weight fr bth f these cplymers, leading t an increase in ethylene ide cntent. The difference in plyurethane prperties that appears when plyl A and plyl B are used t frm the sft segments appears t riginate in differences in the way water is dispersed by these plyls in the frmulatin (13). The decnvlutin results prve that it is the efficient dispersin f water by plyl with randm ethylene ide distributin that is crucial in determining the final plyurethane mrphlgy and prperties. 34 Cellular Plymers, Vl. 22,. 1, 2003
E/umber average P number average P units Influence f Plyether Cplymer Cnfiguratin n Plyurethane Reactin: A Mass Spectrmetry Analysis 90 80 70 60 50 40 30 20 10 2 4 6 8 10 12 14 16 18 E units 0.35 0.3 0.25 0.2 0.15 0.1 0.05 2 4 6 8 10 12 14 16 18 E units Figure 7 a) Cmparisn f number average P units vs. E units in plyl A with the ideal situatin when there is n cmpsitin drift with mlecular weight increases; b) Rati f E units vs. number average P units in plyl A cmpared with the ideal situatin when there is n cmpsitin drift with mlecular weight increases. Data f plyl A are designated by marker, and data in ideal situatin are designated by marker Cellular Plymers, Vl. 22,. 1, 2003 35
E/umber average P number average P units Wu Suen, Jennifer Percy, Shaw L. Hsu, Igr A. Kaltashv and Hward D. Stidham 120 100 80 60 40 20 2 4 6 8 10 12 14 16 18 E units 0.35 0.3 0.25 0.2 0.15 0.1 0.05 2 4 6 8 10 12 14 16 18 E units Figure 8 a) Cmparisn f number average P units vs. E units in plyl B with the ideal situatin when there is n cmpsitin drift with mlecular weight increases; b). Rati f E units vs. number average P units in plyl B cmpared with the ideal situatin when there is n cmpsitin drift with mlecular weight increases. Data f plyl A are designated by marker, and data in ideal situatin are designated by marker 36 Cellular Plymers, Vl. 22,. 1, 2003
Relative Intensity Relative Intensity Influence f Plyether Cplymer Cnfiguratin n Plyurethane Reactin: A Mass Spectrmetry Analysis As shwn in Figure 9, narrw mlecular weight distributins with PDI < 1.05 permit quite brad ethylene ide cmpsitin distributins. Fr plyl A, the PDI was 1.01. Hwever, when 6 ethylene ide units were cplymerized with prpylene ide, the number f prpylene ide units culd range 0.008 0.006 0.004 0.002 35 40 45 50 55 P units 0.008 0.006 0.004 0.002 35 40 45 50 55 P units Figure 9 Distributin f P when E = 6, 9 r 12 units in plyl A. These eperimental values are curve-fitted by a) Pissn distributin; b) Schulz-Zimm distributin. Markers, and designate eperimental values fr relative amunt f P when E = 6, 9 and 12 respectively Cellular Plymers, Vl. 22,. 1, 2003 37
Wu Suen, Jennifer Percy, Shaw L. Hsu, Igr A. Kaltashv and Hward D. Stidham between 31 and 56 while maintaining the PDI at 1.01. This reflects the great cmpsitin hetergeneity fr cplymer plyether samples (26). Further analysis f Figures 9 and 10 shwed that fr randm plyl, prpylene ide distributin was crrelated with ethylene ide distributin, but that this was nt the case fr the blck cplymer. Figure 9 shws that fr mlecules with 6, 9 r 12 ethylene ide units in the randm cplymer, the maimum number f prpylene ide units in the distributin shifts t 42, 45 and 48 respectively. Figure 10 shws that fr the blck cplymer, the maimum in the distributin f prpylene ide units was lcated arund 49, independent f the number f ethylene ide units in the chains. This prbably reflects different pathways in the synthesis f these tw cplymers. Hwever, synthetic details were nt prvided with the plyl samples, and we therefre must refrain frm further cmment. Several studies have crrelated the degree f plymerizatin with kinetics f plymerizatin prcess (33,34). A Pissn distributin was first prpsed by Flry t describe aninic plymerizatin (living plymerizatin) f ethylene ide (35) which has the mathematical frm ν M ( ) = M 1 ep( ν) Γ( M) (2) where (M) is the mle fractin f mlecules with degree f plymerizatin M, Γ(M)is the gamma functin and ν =M n -1.The situatin is much mre cmple fr living cplymerizatin (36). Figures 9a and 10a shw the unsatisfactry result f attempts t fit the data by Pissn distributin.apparently,this mdel fr living plymerizatin f hmplymer is nt applicable t describe the prduct distributin f cplymerizatin. Better results were achieved by curve-fitting with the mre fleible Schultz- Zimm distributin (33,37,38), which has the mathematical frm β M ( ) = z M Mn ep( βm) Γ( Z + 1) z+ 1 1 (3) where Z = M n /(M w -M n ) and β =Z/M n The calculated standard deviatin σ between Schultz-Zimm distributin mdel and the eperimental values was less than that fr Pissn distributin mdel,as summarized in Table 2.The Schultz-Zimm distributin (Z>1) is 38 Cellular Plymers, Vl. 22,. 1, 2003
Relative Intensity Relative Intensity Influence f Plyether Cplymer Cnfiguratin n Plyurethane Reactin: A Mass Spectrmetry Analysis ften used t describe a narrw mlecular weight distributin such as in fractinated samples.the Schulz-Zimm distributin has tw parameters, Z and M n,t cntrl its shape while the Pissn distributin has nly ne, M n,(26,33) and therefre it is less fleible in fitting the data. 0.008 0.006 0.004 0.002 40 45 50 55 60 P units 0.008 0.006 0.004 0.002 40 45 50 55 60 P units Figure 10 Distributin f P when E = 7, 10 r 13 units in plyl B. These eperimental values are curve-fitted by (A) Pissn distributin; (B) Schulz- Zimm distributin. Markers, and designate eperimental values fr relative amunt f P when E = 7, 10 and 13 respectively Cellular Plymers, Vl. 22,. 1, 2003 39
Wu Suen, Jennifer Percy, Shaw L. Hsu, Igr A. Kaltashv and Hward D. Stidham Table 2 Cmparisn f curve-fitting results by Pissn and Schultz-Zimm distributin plyl A E units 6 9 12 n nav 2. 8 n wav 3. 3 4 45. 4 48. 1 4 45. 9 48. 5 Z 90. 0 90. 0 111. 1 p β= Z/ n σ σ.12 nav 2 2.00 2.31-3 -3-4 1.2*10 1.1*10 7.8*10 pissn -4-4 -4 5.4*10 6.8*10 5.5*10 shulz-zimm plyl B E units 7 10 13 n nav 9. 5 n wav 0. 0 4 50. 2 49. 9 5 50. 9 50. 4 Z 100. 0 71. 4 100. 0 p β= Z/ n σ σ.02 nav 2 1.42 2.00-4 -4-4 8.0*10 8.7*10 8.3*10 pissn -4-4 -4 7.1*10 8.2*10 8.0*10 shulz-zimm CCLUSIS The analysis f MALDI-TF mass spectra prvides imprtant structural infrmatin fr sft segment plyether plyls used in plyurethane fam frmulatins. In additin t infrmatin n the mlecular weight distributin, 3-dimensinal decnvlutin f the high reslutin spectra als prvides a quantitative descriptin f the abundance f each plymer chain as a functin f its cmpnent hydrphilic ethylene ide and hydrphbic prpylene ide units. The results indicate cmpsitin drifts in bth the randm and blck cplymer plyls, and as plymer chains becme lnger, the ethylene ide cntent increases. The distributin f ethylene ide is dependent upn prpylene ide distributin fr randm cplymer, but is independent fr 40 Cellular Plymers, Vl. 22,. 1, 2003
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