Long-chain hyperbranched comb-block copolymers: synthesis, microstructure, rheology and thermal behavior

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1 Supporting Information for Long-chain hyperbranched comb-block copolymers: synthesis, microstructure, rheology and thermal behavior Carlos R. López-Barrón, Patrick Brant, Maksim Shivokhin, Jiemin Lu, Shuhui Kang, Joseph A. Throckmorton, Trent Mouton, Truyen Pham and Rebecca C. Savage ExxonMobil Chemical Company, Baytown, Texas 77520, USA Ethylene acrylic acid copolymer The EAA was characterized by differential scanning calorimetry (DSC) and 1 H NMR. The 1 H NMR spectrum for this EAA is shown in Figure S1. The resonance at 2.41 ppm is due to the backbone hydrogen H a denoted in the figure. The sharp resonance at 1.35 ppm is from contiguous ethylene runs, (CH 2 ) x, in this hyperbranched polymer. Other resonances are due, in part, to the variety of other aliphatic hydrocarbon branches as well as end groups from eg. peroxide initiator fragments. Figure S1. 1 H NMR spectrum of ethylene acrylic acid copolymer (EAA) in TCE-d 2 solvent.

2 Vinyl terminated atactic polypropylene All three vt app samples used in this study were made by homogeneous coordination polymerization of propylene using pentamethylcyclopentadienyl 1,3 dimethylindenyl hafniumdimethyl activated with dimethylanilinium perfluorotetranaphthylborate. The details of synthesis and characterization are documented elsewhere. 1, 2 The basic structure of each vt app sample is conveyed in the schematic below. Schematic S1. The vt-app samples made with this homogeneous catalyst have been shown to be comprised of 95-99% vinyl terminated polymer chains depicted in the schematic. For illustration, the 1 H NMR spectrum of one vt app sample, vt-app-1k, used in this work is provided in Figure S2. Figure S2. 1 H NMR (298 K, 400 MHz) spectrum of ally terminated app in TCE-d 2 solvent. Multiplet resonances at 5.63 and 4.98 ppm (integration 1:2) are assigned to the vinyl terminus. A very weak nearly symmetric doublet at 4.73 and 4.62 ppm is due to vinylidene termini. The terminal vinylidene accounts for ~2-3% of all unsaturations, while the symmetric internal vinylidene accounts for less than 1% of all unsaturations. (*) due to a small quantity of toluene from the catalyst solution. 2

3 The number average molecular weight of each pure vt-app sample is calculated with equation S1. The values calculated are given in Table S1. Molecular weight moments of these samples are also measured by GPC-DRI and M n and M w values are also provided in Table S1. The values are based on calibration against an isotactic polypropylene standard. These samples contain ~55% r diads, so a more accurate (about 10% bigger) molecular weight values can be obtained versus an atactic-polypropylene standard. M n = 14 ( all protons ) terminal olefin 4.98 ppm (S1) Table S1. Number average molecular weights (Mn) from 1 H NMR and Molecular Weight Moments from GPC-DRI of vt-app samples used in preparations Vt-aPP 1 H NMR GPC-DRI* Mn Mn Mw app-1k app-3k app-6k *ipp standard Hydroxyl terminated atactic polypropylene The syntheses of the app-oh samples follow a procedure described in Dalsin et al. 3, 4. The 1 H NMR spectra of the three appoh samples used for syntheses of EAA comb block copolymers are shown in Figures S3 - S5. Example Synthesis of app-oh. A clean, dry 1 L single neck round-bottom flask equipped with a stirring rod was assembled in a nitrogen purged dry box. Vt-aPP-1k) (5.5 g, 4.75 mmol) and THF (20 ml) were added to the flask. The mixture was placed in the refrigerator (~ -20 o C) in the drybox for 30 min before the addition of 9-Borabicyclo[3.3.1]nonane (9-BBN) (0.5 M solution in THF, ml, mmol) by syringe. This reaction mixture was stirred at 25 o C for 12 hr. It was then transferred from the dry box to a hood. The nitrogen purged reaction mixture was cooled to -20 o C before the sequential slow addition by syringe of methanol (6 ml), 6 N NaOH (10 ml, 60 mmol) and H 2 O 2 (30 wt%, 14 ml, 221 mmol) by syringe. After the addition was finished, the reaction mixture was gradually heated up to 40 o C and kept at that temperature for 4 hr. The resulting solution was cooled to room temperature and the solvents were stripped by rotovap at 40 o C. The white gluey residue was then dissolved in hexanes (50 ml), partitioned 3

4 with weak acidic water (ph=5, 50 ml x 1), followed by deionized water (50 ml x 3). The organic layer was dried over MgSO 4, filtered, and finally concentrated with a rotovap at 40 o C to afford a cloudy oil. This product was dried at 40 o C in a vacuum oven overnight to completely remove the solvents (and perhaps the lowest molecular weight app-oh fraction) thus affording a colorless oil of desired product appoh-1k (5.53 g, 4.7 mmol, 99 % recovery). The 1 H NMR spectrum of this product is shown in Figure S5. The spectrum shows the disappearance of the olefinic resonances and appearance of the CH 2 -OH resonance at 3.62 ppm. Figure S3. 1 H NMR (298 K, 400 MHz) spectrum of app-oh-1k in TCE-d 2 solvent. This and other alcohols made by oxidative hydroboration of vinyl terminated app. Triplet resonance at 3.58 ppm is due to Polypropylene- CH 2 CH 2 CH 2 -OH terminus. The (*) is due to adventitious water. 4

5 Figure S4. 1 H NMR (298 K, 400 MHz) spectrum of app-oh-3k in TCE-d 2 solvent. Triplet resonance at 3.58 ppm is due to Polypropylene- CH 2 CH 2 CH 2 -OH terminus. 5

6 Figure S5. 1 H NMR (298 K, 400 MHz) spectrum of app-oh-7k in TCE-d 2 solvent. Triplet resonance at 3.58 ppm is due to Polypropylene- CH 2 CH 2 CH 2 -OH terminus. The (*) is due to adventitious water. As with the vt-app s we measure M n s of the app-oh samples from their 1 H NMR using equation (S1) but now the denominator is the integral of the primary alcohol -CH 2 -OH terminus. The number average molecular weights for the alcohols are given in Table S2, along with their glass transition temperatures and molecular weights measured by GPC-DRI. 6

7 Table S2. Number average molecular weights (M n ) from 1 H NMR and T g s of appoh products Sample M n, g/mol (1H NMR) T g, C (DSC) M n (GPC-DRI) M w appoh-1k appoh-3k appoh-7k EAA-cb-aPP copolymers An example of the 1 H NMR spectra recorded for the EAA-cb-aPP ester products, EAA-cb-aPP-3k-40, is shown in Figure S6. The spectrum shows the desired ester multiplet peak (of O=C-O-CH 2 of the EAAaPP ester) at 4.10 ppm and absence of the alcohol peak at (CH 2 -OH end unit of the app-oh) at 3.65 ppm, as well as the methine peak at 2.35 ppm associated with the ester (methine from acrylic acid at 2.41 ppm). No unidentified peaks were observed. Not all samples dissolved fully in the NMR tube (very small fluffy insoluble fraction in bottom of tube). This correlated with development of slight tan or brownish color over time at the high temperature. 7

8 Figure S6. 1 H NMR (393 K, 500 MHz) spectrum of EAA-cb-aPP-3k-40 in TCE-d 2 solvent. Insert: Blow-up of ppm region shows the resonances associated with the ester and acid structures. Singlet at 2.49 ppm is from residue of xylenes reaction solvent. Multiplet at 2.6 ppm is assigned to a peroxide initiator fragment (observed in other peroxide initiated high pressure free radical polymer products). Peak labeled PE at 1.35 ppm is from EAA. Gel permeation chromatography with multiple detectors (GPC-4D) was performed on the parent EAA, the vt-apps, and two EAA-cb-aPP samples. It is well known that high temperature GPC of crystallizable EAA copolymers and terpolymers made by high pressure free radical polymerization is generally problematic. These copolymers containing acrylic acid typically suffer some loss during the filtration step and further loss during elution on the column. Polymer chains that do not elute following standard GPC methodology may instead slowly bleed from the column or become stuck on the column permanently changing its calibration. Through full esterification of such samples with eg 8

9 diazomethane the quantitation is greatly improved and the potential for damage to the columns reduced. The EAA and the comb blocks prepared in this study were not fully esterified, and so consequently mass recoveries are relatively low and risk of damage to the column is significant. Nonetheless, three GPC-4D chromatograms were recorded and, together with chromatograms of app starting materials, these chromatograms provide important independent structural information relevant to the purity of the comb blocks. First, it is necessary to emphasize the purity of the precursors. Carbon NMR shows that linear vinyl terminated app macromonomers made with this catalyst under homogeneous polymerization conditions are nearly free of unreactive fully saturated structures typified by structures such as iii and iv below. i ii iii iv The conversion of each vt app (including the small quantity of terminal vinylidene) to app-oh is virtually quantitative based on 1 H NMR of the isolated alcohol products. In the grafting step, reaction of appoh with EAA results in loss of the alcohol signal (not detectable) and commensurate appearance of the ester signal associated with the comb block. These findings together with supporting GPC-4D data below indicate the product structures can be assigned to be the EAA-cb-aPP s, and that they are free of significant 9

10 low molecular weight impurities such as app or appoh that would compromise the interpretation of the rheology and other data. GPC-4D Analyses The molecular weight, the propylene comonomer content (C2%) and the long chain branching index (g ) are determined by using a high temperature Gel Permeation Chromatography (Polymer Char) equipped with a multiple-channel band-filter based Infrared detector IR5, an 18-angle light scattering detector (Wyatt Technology) and a 4 capillary Wheaton-bridge viscometer (Agilent). Three Agilent PLgel 10µm Mixed-B LS columns are used to provide polymer separation. Aldrich reagent grade 1,2,4-trichlorobenzene (TCB) with 300 ppm antioxidant butylated hydroxytoluene (BHT) is used as the mobile phase. The TCB mixture is filtered through a 0.1 m Teflon filter and degassed with an online degasser before entering the GPC instrument. The nominal flow rate is 1.0 ml/min and the nominal injection volume is 200 L. The whole system including transfer lines, columns, detectors are contained in an oven maintained at 145 C. Given amount of polymer sample is weighed and sealed in a standard vial with 80 L flow marker (Heptane) added to it. After loading the vial in the autosampler, polymer is automatically dissolved in the instrument with 8 ml added TCB solvent. The polymer is dissolved at 160 C with continuous shaking for about 2 hour. The conventional molecular weight is determined by combining universal calibration relationship and Mark-Houwink equations with the column calibration which is performed with a series of monodispersed polystyrene standards ranging from 700 to 10M. The Mark-Houwink parameters K/α are /0.67 for polystyrene and /0.705 for all the app and EAA samples. 10

11 The comonomer composition is determined by the ratio of the IR5 detector intensity corresponding to CH 2 and CH 3 channel calibrated with a series of PE and PP homo/copolymer standards whose nominal value are predetermined by NMR or FTIR. The LS molecular weight (M) at each point in the chromatogram is determined by analyzing the LS output using the Zimm model for static light scattering. The refractive index incremental dn/dc is for all the EAA polymers. The branching index (g' vis ) is calculated as [ ] g' vis, where the average intrinsic viscosity, [ ] avg, of the sample is calculated by km avg v ci i ci [ ] and the M v is the viscosity-average molecular weight based on molecular weights avg determined by LS analysis. The K/α = /0.695 are the M-H parameters for polyethylene which is used as a reference polymer here. GPC-4D recorded on selected samples also provides independent evidence for the quantitative or nearly quantitative attachment of appoh to the EAA. Comparisons of high temperature gel permeation chromatograms recorded with multiple detectors (GPC-4D) are provided in Figures S10 and S11. In each comparison, the chromatograms for EAA and the appropriate vt-app precursor are provided for the corresponding comb block: EAA-cb-aPP-3k-40 and EAA-cb-aPP-6k-60. Of particular importance in these two comparisons is the apparent propylene content ( C3 is defined as the propylene weight fraction over the whole molecules in an EP copolymer. Therefore, the C3 is 100% for PP and 0% for PE. For non-ep copolymer such as EAA, the C3 is not the actual propylene content but a number corresponding to the balance between C2 and the comonomer AA (there is a monotonic relationship between AA content and the C3 value) as a function of logm. 11

12 Figure S7. Comparison of GPC-4D for EAA (blue), vt-app-3k (blue), and EAA-cb-aPP-3k-40 (red). Left ordinate provides eluted mass as a function of logm and the right ordinate provides wt% propylene (C3) as a function of logm. Figure S8. Comparison of GPC-4D for EAA (blue), vt-app-6k (blue), and EAA-cb-aPP-3k-60 (red). Left ordinate provides eluted mass as a function of logm and the right ordinate provides wt% propylene (C3) as a function of logm. 12

13 In these GPC-4D comparisons, the propylene content for vt-app-3k and vt-app-6k is 94.8 and 95.6%; respectively (based on known compositions and microstructure, expected value is ~100%). The apparent propylene content for the EAA is 19%, or far less than the values for the vt-app s. The non-zero value for EAA is due, in part, to the plethora of different aliphatic branches (methyl, ethyl, isoamyl, butyl along with other branches) also present in high pressure free radical products. GPC-4D of polyethylene homopolymer products yields propylene contents in the 0-2 wt% range. Nonetheless, the GPC-4D chromatograms for these precursors establish the upper and lower limits of propylene content as calculated by this infrared algorithm. If the app-oh precursor is attached to the EAA via esterification we expect to see a fairly uniform distribution of propylene across the molecular weight distribution in the EAA-cb-aPP product and in particular extending to high molecular weights (>50kD). In the two comb blocks examined EAA-cb- 3k-40 (Figure S5), and EAA-cb-aPP-6k-60 (Figure S6) the wt% C3 is relatively constant or increases as a function of logm, and is reasonably commensurate with the bulk quantity of app in the sample: EAA-cb- 3k-40 (46.5 wt% C3 by GPC-4D) and EAA-cb-aPP-6k-60 (61.7 wt% C3 by GPC-4D). Thus, in the two comb block cases examined, the grafting efficiency of appoh to EAA is calculated to be >95%.and the results are consistent with, or complement, the 1 H NMR data. 13

14 Figure S9. WAXS peak analysis for the EAA and EAA-cb-aPP copolymers. WAXS data was fitted with two amorphous Gaussian peaks and three Crystalline Gaussian peaks. The cumulative fit is the sum of amorphous and crystalline peaks. 14

15 Figure S10 AFM micrograph at 25 C for the EAA copolymer. 15

16 Figure S11. van Gurp-Palmen plots of for the EAA and EAA-cb-aPP copolymers grouped as (a) varying side chain length and (b) varying app content. Note that in the van Gurp-Palmen plot representation, linear polymers show a monotonic decrease of the shift angle with complex modulus, whereas longchain branching produces a kink, or shoulder, which marks the onset of the longer relaxation related to the whole polymer. 5 This delay is due to the topological constrains imposed by the long branches to the motion of the backbone. 16

17 Table S3. Discrete relaxation spectrum fitting parameters for compatibilized EAA and EAA-cb-aPP copolymers. EAA EAA-cb-aPP 1k-40 EAA-cb-aPP 3k-40 i g i, Pa i, s g i, Pa i, s g i, Pa i, s e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e+002 EAA-cb-aPP 7k-13 EAA-cb-aPP 7k-40 EAA-cb-aPP 7k-60 i g i, Pa i, s g i, Pa i, s g i, Pa i, s e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e