Catalytic Activity of a Titanium(IV)/Iron(II) Heterometallic Alkoxide in the Ring‑Opening Polymerization of ε-Caprolactone and <i>rac</i>-Lactide

Giese, Siddhartha O. K.; Egevardt, Cristiano; Rüdiger, André Luis; Sá, Eduardo L.; Silva, Thiago Alessandre; Zawadzki, Sônia F.; Soares, Jaísa F.; Nunes, Giovana G.

doi:10.5935/0103-5053.20150214

Acessibilidade / Reportar erro

Brasil

Journal of the Brazilian Chemical Society

Español English

Brasil

Español English

sumário « anterior atual seguinte »

Sumário

Articles • J. Braz. Chem. Soc. 26 (11) • Nov 2015 • https://doi.org/10.5935/0103-5053.20150214 copy

Catalytic Activity of a Titanium(IV)/Iron(II) Heterometallic Alkoxide in the Ring‑Opening Polymerization of ε-Caprolactone and rac-Lactide

Authorship SCIMAGO INSTITUTIONS RANKINGS

The activity of the heterometallic alkoxide [FeCl{Ti₂(OⁱPr)₉}] (1) towards polymerization of rac-lactide (rac-LA) and ε-caprolactone (ε-CL) was investigated in toluene solution and in bulk at various temperatures, monomer/heterometallic alkoxide molar ratio and reaction times. The alkoxide 1 was active in solution for ε-CL and in bulk for both monomers. Polymers were obtained in good yields with molecular weights ranging from 3890 to 15000 g moL^-1 and polydispersity indexes (PDI) values varying from 1.3 to 2.5. Based on the ¹H nuclear magnetic resonance (NMR) end-group analysis of polymers, a coordination-insertion mechanism was suggested for both monomers. The average number of growing chains per molecule of initiator (4 to 5 for rac-LA and 7 to 8 for ε-CL) indicates that both bridging and terminal isopropoxides are active initiating groups. Kinetic studies with ε-CL indicated that the polymerization rate is first order with respect to monomer concentration. The catalytic properties of 1 were compared to those found for other titanium(IV) and iron(II) complexes using ε-CL as a model monomer.

Keywords:
heterometal alkoxide; ring opening polymerization; ε-caprolactone; rac-lactide; iron(II), titanium(IV)

entry	ε-CL/1^a a Monomer to initiator molar ratio. The monomer concentration used for solution polymerization was 8.76 mol L -1. Also, initiator concentrations in mmol L-1 were as follows: for ε-CL/1 = 250: 35 mmol L-1; ε-CL/1 = 500: 17.5 mmol L-1; ε-CL/1 = 1000: 8.8 mmol L-1 and ε-CL/1 = 1500: 5.8 mmol L-1;	T / °C	time / h	α_c / %	Yield^b b yield based on the isolated amount of solid; / %	M_n (theoretical) ^c c theoretical molecular weight calculated from the formula: [MW(CL) × (CL/1) × αc] + 60 (for the terminal groups); /(g mol^-1)	M_n (¹H NMR)^d d average molecular weight determined by 1H NMR; /(g mol^-1)	M_n (GPC)^e e average molecular weight determined by gel permeation chromatography (GPC) and multiplied by the correction value of 0.56;32 /(g mol^-1)	PDI^f f polydispersity index determined by GPC;	N_n^g g calculated from Mn(theoretical)/Mn(GPC). It refers to the average number of growing chains per molecule of the initiator. Blank = experiment carried out in the absence of 1.
Blank	−	120	48	3	−	−	−	−	−	−
1	500	30	8	86	77	55928	6280	6900	1.61	8.0
2	500	60	8	99	93	63948	7760	8030	1.61	8.0
3	500	90	8	99	98	63948	9470	9080	1.60	7.0
4	500	30	12	89	66	57640	4570	7740	1.59	8.3
5	500	60	12	99	96	63948	6280	8160	1.60	7.8
6	500	90	12	99	81	63948	7070	8760	1.56	7.3
7	250	90	8	99	89	35098	4100	7000	1.62	5.0
8	1000	90	8	99	89	119846	10670	9600	1.58	12.5
9	1500	90	8	99	99	176365	12600	14390	1.99	12.3
10	500	30	24	90	85	58208	3100	3900	1.77	14.9
11	500	60	1	97	75	62202	7880	7490	1.59	8.3
12	500	90	0.5	98	83	63948	7730	9090	1.53	7.0
13	500	90	1	98	98	62773	8790	8630	1.51	7.3
14	500	120	0.08	99	95	63948	6730	7780	1.55	8.2
15	250	90	0.5	99	80	35098	4400	6800	1.65	5.2
16	1000	90	0.5	99	90	119846	11240	9880	1.65	12.2
17	1500	90	0.5	99	95	176365	18310	6100	2.46	28.9

entry	rac-LA/1^a a Monomer to initiator molar ratio. Initiator concentrations in mmol L-1 were as follows: rac-LA/1 = 250 (27.7 mmol L-1), rac-LA/1 = 500 (13.9 mmol L-1), rac-LA/1 = 750 (9.3 mmol L-1), rac-LA/1 = 1000 (6.9 mmol L-1);	Temperature / °C	time / h	α_c / %	Yield^b b yield based on the weight of isolated solid; / %	Mn (theoretical)^c c theoretical molecular weight calculated from the formula: [Mw(LA) x (LA/1) × αc] + 60 (for the terminal groups); / (g mol^-1)	Mn (GPC)^d d average molecular weights determined by GPC, considering the correction value of 0.58;32 /(g mol^-1)	PDI^e e polydispersity index calculated from GPC data;	Nn^f f calculated from Mn(theoretical)/Mn (GPC). It refers to the average number of growing chains per molecule of the initiator. Blank = experiment carried out in the absence of 1.
Blank	−	130	24	0	0	−	−	−	−
18	250	130	1	96	90	34650	7980	1.49	4.3
19	500	130	0.08	87	76	62760	12180	1.37	5.1
20	500	130	1	95	85	68520	12970	1.37	5.3
21	500	130	2	100	98	72125	14030	1.37	5.1
22	500	160	1	96	85	69240	13090	1.37	5.3
23	750	130	1	93	82	100590	14350	1.32	7.0
24	1000	130	1	75	68	108160	14270	1.30	7.6
25	1000	130	2	84	78	121130	14980	1.31	8.1

Temperature / °C	k_p / min^-1 (ε-CL/1= 500)	k_p / min^-1 (ε-CL/2= 250)	k_p1/k_p2
90	0.168	0.605	3.6
100	0.304	1.483	4.9
110	0.525	2.177	4.1
120	2.903	3.993	1.4
130	4.463	6.053	1.4

Sociedade Brasileira de Química Instituto de Química - UNICAMP, Caixa Postal 6154, 13083-970 Campinas SP - Brazil, Tel./FAX.: +55 19 3521-3151 - São Paulo - SP - Brazil
E-mail: office@jbcs.sbq.org.br

Acompanhe os números deste periódico no seu leitor de RSS

[1] *e-mail: nunesgg@ufpr.br